Acta Energetica Power Engineering Quarterly no. 01/2009 by ENERGA SA

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nergetica

01/2009

number 1/year 1

Electrical Power Engineering Quarterly

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Patronage Gdańsk University of Technology

ENERGA S.A.

Editor-in-Chief Zbigniew Lubośny

Academic Consultants Janusz Białek / Mieczysław Brdyś / Antoni Dmowski / Istvan Erlich / Andrzej Graczyk Tadeusz Kaczorek / Marian Kaźmierkowski / Jan Kiciński / Jerzy Kulczycki Kwang Y. Lee / Zbigniew Lubośny / Jan Machowski / Om Malik / Jovica Milanovic Jan Popczyk / Zbigniew Szczerba / G. Kumar Venayagamoorthy / Jacek Wańkowicz

Editorial Staff Office Acta Energetica

ul. Grodzka 12, 80-841 Gdańsk, POLAND tel.: +48 58 320 00 94, fax: +48 58 320 00 90 e-mail: redakcja@actaenergetica.org www. actaenergetica.org Graphic design Mirosław Miłogrodzki

Translation Maria Stelmasiewicz Witold Zbirohowski-Kościa

Proofreading Mirosław Wójcik

Editorial Support Katarzyna Żelazek

ISSN 2080-7570

nergetica

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Electrical Power Engineering Quarterly

Content 8

INNOVATIVE POWER INDUSTRY. ECOLOGICAL-POWER ENGINEERING AND ECONOMIC -CIVILISATION CONTEXT

Jan Popczyk 24

CURRENT DISTORTION IN LIGHTING SYSTEMS AND ITS IMPACT ON POWER SUPPLY INSTALLATIONS

Stanisław Czapp 40

DEVELOPMENT OF CO2 EMISSION TRADING IN THE EUROPEAN UNION

Andrzej Graczyk 48

CONDITIONS FAVOURING VOLTAGE AVALANCHE IN THE OPERATION OF GENERATOR REGULATORS – SELECTED ISSUES

Jacek Klucznik / Robert Małkowski / Piotr Szczeciński / Ryszard Zajczyk 58

POWER LOSSES AS NECESSARY OWN NEEDS OF NETWORK

Jerzy Kulczycki / Michał Rudziński Waldemar Szpyra 78

ANALYTICAL DERIVATION OF PSS PARAMETERS FOR GENERATOR WITH STATIC EXCITATION SYSTEM

Zbigniew Lubośny / Janusz W. Białek 94

PPN - LIVE CONDUCTOR OPERATIONS ON 400 KV, 220 KV AND 110 KV OVERHEAD TRANSMISSION AND DISTRIBUTION LINES IN ENERGA-OPERATOR S.A. TORUŃ BRANCH.

Ryszard Michniewski 104

MEASUREMENT OF PARTIAL DISCHARGES IN MEDIUM VOLTAGE CABLE LINES

Sławomir Noske

Gdańsk University of Technology is the oldest and the largest technical college in the North of Poland. Its origins go back to the autumn of 1904, when the Royal Technical College (Königliche Technische Hochschule) was founded. It was the first academic school in Gdańsk. Its goal was to spread technical knowledge in the West Prussia and Pomeranian area. From the very beginning the school was located in the beautiful buildings designed by Albert Carsten, built between 1900 and 1904 and well preserved until today. The college was to educate 600 students in the first years of its operation. All in all, about sixteen thousand students were matriculated until 1945. After World War II, on May 24, 1945 Gdańsk University of Technology, the first Polish state college was founded by virtue of the decree of State National Council. The citizens started renovation of the premises ruined and burnt during the War already in April 1945. The teachers, including many distinguished professors, came mainly from Lvov, Vilnius and Warsaw. At present Gdańsk University of Technology has 9 faculties, 7 of which have full academic rights. About 24 000 students are studying at 27 specialisations, 3 of which are interdepartmental and 1 - intercollegiate. Gdańsk University of Technology provides education on engineer, master and doctoral levels in all fields of science, starting from civil engineering and architecture, our oldest specialisations, to modern electronic engineering, material nanotechnology, biotechnology or biomedical engineering. Economics, business administration and social sciences seem to naturally complete the studies in technical fields. Our school confirms its well established reputation of a strong educational, scientific and cultural centre by cooperating with other universities and research institutions in Poland and abroad. We cooperate with many companies, educational and cultural organisations and state agencies in the ambition to create a good image of Gdańsk, Pomerania, Poland and Europe. Cooperation between Gdańsk University of Technology and the region’s business community is getting stricter and stronger every year. We are closely related particularly to the Pomeranian Chamber of Commerce and to science and technology parks. Our goal is to stimulate cooperation so that the scientific community’s achievements could be effectively applied in economy. Each year the college very actively participates in the “Industrial Technology, Science and Innovation Fair” held in the Gdańsk International Fair Co., where we present innovative solutions and their applications in the economic environment. We also win many medals and awards. It is the graduates of Gdańsk University of Technology that create the school’s unique character and reputation. They manage industries and take part in the formation of our country’s present and future. They conduct research in science centres and create new 21st century technologies. We have all the reasons to claim that Gdańsk University of Technology’s diploma can pave the way to professional success and to realisation of one’s aspirations. Let us achieve our basic goals with imagination and wisdom. Therefore, I ask you all to take up new challenges, indispensable for further development of our college in the age of constantly changing environment and global competition. Cooperation between Gdańsk University of Technology and ENERGA Energetic Concern in the field of power industry is one of such challenges. The newly-founded scientific and technical magazine Acta Energetica constitutes a synergic result of our cooperation. May the authors of this magazine enjoy its every success and the readers - a pleasant and instructive reading. Prof. Henryk Krawczyk Rector of GUT

The European power industry is undergoing an enormous transformation. There are two goals: to increase power supply security and at the same time to reduce the environmental impact. These priorities express our care about the present as well as about the future. It will be difficult to make them a reality because it requires from the power industry companies to get involved in projects which some stockholders might consider controversial. Our cooperation with the science community shall support this kind of involvement. That is why ENERGA Group together with Gdańsk University of Technology has founded Acta Energetica magazine. Its first issue is right in your hands. Innovativeness is the key concept for the development of such a company as ENERGA. We consider this notion in a far broader way than only being ready to buy new technologies. We want to participate in their creation. We also want to explain the consequences of formal regulations and postulate their change for the benefit of our customers. By stimulating development of certain areas of power industry we wish Acta Energetica to support popularization, both in Poland and abroad, of the research carried out by the scientists, particularly at the Gdańsk University of Technology. We would like this magazine to contribute to faster implementation of new technical and technological solutions in ENERGA Group. The technical ideas of both institutions should become visible in various scientific and economic environments. That is why I encourage you to read Acta Energetica. Mirosław Bieliński President of the Board of ENERGA S.A.

WHAT ARE OUR OBJECTIVES? The challenges of contemporary electrical power systems are the challenges of Acta Energetica ▶ Controlling power engineering subsystems highly saturated with dispersed sources, i.e. intelligent systems • Development of IT systems for distribution system operators to control dispersed sources, distribution systems and consumers (electric power consumption control), • Control algorithms for dispersed sources, • Control algorithms for distribution systems to eliminate dynamic overload of system elements, • Technical systems for controlling power demand including kW-meters with two way communication, • Electrical power engineering protection automation for this kind of system, • New systems. ▶ Accumulation technologies and application of electrical power in electrical power engineering systems ▶ Electricity driven cars • Sources of energy for electric cars, i.e. batteries, supercapaciters/condensers, • Using electric cars as dispersed electrical energy accumulators in the electrical power engineering system, • Developing a system of stations for charging cars and algorithms for their control, using electric cars as dispersed power accumulators. ▶ Fuel cells • Fuel cell technologies and the possibility of their application in electrical power engineering systems, • Using fuel cells as an element of power accumulators, • Cogeneration system type accumulators: fuel cell + wind farm, fuel cell + PV source and others, e.g. applied in transport, • Fuel cell control algorithms in various work configurations for the needs of electrical power engineering systems. ▶ Protection and reconstruction of the electrical power engineering systems • Automation of autogenic frequency unloading – SCO • Automation of autogenic voltage unloading – SNO • Autonomic dispersed electrical power engineering protection systems for individual consumers – an equivalent of SCO and SNO system automatics • Control algorithms for dispersed sources, including dispersed sources in protection and reconstruction of power engineering systems. ▶ System services in distribution systems • Distribution system operator as the contracting party concentrating system services on the local market (in sub systems), • Distribution system operators as suppliers of system services to the distribution system operator. ▶ Integration of electrical power and gas engineering systems as an element of the power safety segment • Development of gas and biogas source technologies, • Cooperation capacity of electrical power and gas engineering systems to cover fluctuating demand (periodical shortage), • Algorithm for integrated control of a gas and electrical power engineering systems. ▶ Monitoring and managing the electrical power line load • New technologies and methods for expanding the capacity of electrical power lines, • Systems and devices for monitoring the dynamic load of electrical power lines • Communication systems for management centres with electrical power line measuring systems, • Algorithms for managing the electrical power line load. All the topics referred to above are obviously linked with the financial aspect of economic efficiency and – as an element of effectiveness – national and possibly international legal environment.

We are the witnesses of a turbulent transformation in the sector of power systems, including electric power engineering systems. This fact inspired the appearance of a new scientific journal – Acta Energetica. May you live in interesting times – is the curse cast by the ancient Chinese on their enemies. Whether we like it or not we do live in interesting times, also interesting for power engineering. We believe that the curse can turn to a blessing. Continuous development characterises above all, though not exclusively, energy sources. Renewable energy resources such as wind farms and biogas and solar power plants, minor photovoltaic cells and fuel cells are being introduced on a global scale. We face the era of electricity driven cars, marine transport supported by wind power and new fuel saving aviation constructions. Changes are also expected in electric power transmission systems. Thermonuclear reactors under construction today should provide the opportunity to obtain more energy produced than fed to the systems. Contemporary times are the times of transformations, which means that it is advisable and relatively easy – thanks to social acceptance and governmental financing trends – to get drawn into the development drive in the electric power engineering sector. Scientific and research centres are naturally predestined in this area, as the key creators of the concept, as are the institutions managing electric power engineering systems, power supply companies, system operators, and providers to the energy sector and power engineering companies. Practical application of theory and concepts developed in scientific research centres creates the quality of life and contributes to the development of society. The experience of companies involved in power engineering (electric power) should not be underestimated. It is an imperative of our times to start this new scientific journal – Acta Energetica. The publication has its roots in the power engineers’ circles combining – thanks to Gdańsk University of Technology and Energa Group – the best in the scientific sphere and in practical applications. We would like to present new ideas, to solve technical, technological, organisational, managerial and economic problems in the power sector. Our publication is addressed to engineers and other technical staff, managerial staff, university staff and students involved in power and electric power engineering. The first issue of Acta Energetica, as an example of the topics covered by the journal, presents articles on various electrical engineering issues. We begin with a paper discussing the problems of modern electric power systems and predicting their development. The two other articles are on stability of electrical power system and its components with a decisive impact on the stability, i.e. AVRs and PSSs. Medium voltage networks issues are represented by an article on power and energy losses in electrical power systems (initiating a series of articles devoted to operational problems of medium voltage grids) and a paper on electric arc in MV switchboard modelling. Low voltage problems are represented by an article dealing with deformations of current consumed by lighting devices. The articles devoted to power systems practice refer to measuring partial discharges on medium voltage cable lines and maintenance operations on 400 kV transmission lines. Economic issues are represented by an article on CO2 emission trading in the European Union.

You are cordially invited to partake in our endeavours. Zbigniew Lubośny Editor in Chief of Acta Energetica

Jan Popczyk / Silesian University of Technology

Authors / Biographies

Jan Popczyk Gliwice / Poland A graduate of the Electrical Engineering Faculty at Silesian University of Technology (1970), he obtained his doktor degree [PhD – first level doctorate] four years later and the title of professor in 1987. He was a co-author of the reform of the Polish electric power engineering sector and in the first half of the nineties implemented the reform as the President of Polish Electric Power Supply Systems]. He participated in the process of connecting the Polish power system with the systems of Central and Western Europe. He was also involved in the establishment of four micro firms and their management – as President of Management Board and President of Supervisory Board at the post of Company President or Chairman of the Supervisory Board. In 2005, together with a group of students, he developed the concept of a virtual network e-GIE (e-Gmina Infrastruktura Energetyka), which is a tool combining civilisation development of Polish municipalities with the activeness of the young generation of university graduates and supporting the restructuring of the infrastructural sectors, mainly the power, heating and gas sectors. Since 2007, he has been supporting the Energy and Climate Package 3x20 (Cluster 3x20). He is a member of many professional associations.

INNOVATIVE POWER INDUSTRY. Ecological-power engineering and economic-civilisation context

INNOVATIVE POWER INDUSTRY. Ecological-power engineering and economic-civilisation context Jan Popczyk / Silesian University of Technology

The reforms based on TPA principle launched in 1990 by Great Britain [4] still continue to determine the perspective in which we perceive the condition of electric power industry. The real significance of those reforms consisted in making the general public aware of the fact that competition in electric energy market is theoretically possible. The practical meaning of the reforms, however, consists nowadays in the fact that they revealed a system conflict between the superstructure (power policy, that is political-corporate business alliance [5]) and the basis (knowledge society) in the system of supplying the economy with fuels and energy to three final markets (of electric energy, heat and transport). Such a conflict, of course, does not arise in a short period of time, and is not characteristic only for Poland. However, this conflict poses a much bigger threat to Poland than to other countries. It also results in a much more significant loss of opportunities that each big crisis provides. All that means that the approach telling the society to adapt to the ways of power industry functioning must be changed. And adapting of power industry to the standards of knowledge society must be encouraged (two decades should be enough to complete the process). The industry must also be prepared to function in noemission/hydrogen society (fourth, fifth decade of this century)1. In a mature knowledge society and in the future no-emission /hydrogen society one must make a clear distinction between electric power system and the system of supplying economy with fuels and energy. The consolidation made in Poland by the previous government, and continued by the current government, unfortunately is an imitation of declining patterns of industrial society and a movement against the current. It means corporate, historical and technological isolationism. Corporate isolationism prevents the convergence so much needed in knowledge society (in the area of all sectors of fuels and energy). Historical isolationism means no present capacity for critical use of past experience. Generally speaking, it means the first great allocation of resources in power industry from supply to demand orientation and the first great stage of internalisation of external environmental costs (concerning dust and SO2)emission). It refers In particular to four traumatic American experiences from the 1960s and the 1970s [6]2 that were a catalyst for market reforms of electric power industry in the 1980s (developing new forms of financing investments in the sector of independent producers – USA3, South America) and in the 1990s (privatisation-liberalisation reforms, creating competition based on the use of 1 A global political project, with hydrogen energy technologies (fuel cell in particular) as its symbol, and CO2 emission reduction (against the current level) at least by 50% (in countries/regions – world leaders of development – even by 80%). 2 The north-eastern blackout – 1965 (implementation of the principle of enhancement of structural reliability of transmission networks by redundancy), first oil crisis – 1973/74, stock exchange crisis Consolidated Edison – 1974, Three Mile Island failure – 1979). 3 Effective introduction of legislative procedure connected with PURPA Bill, lasting for 4 years – 1978–1982, made way for development of American segment of independent producers (IPP), cogeneration oriented (environmental protection and reduced use of primary fuels).

Abstract Wars are fought for land, religion, natural resources, water and sources of energy. Man has always needed land to feed himself. And in Europe land has always been scarce in terms of foodstuffs supply security. That is why over fifty years ago the Treaties of Rome (actually one of them, establishing the European Economic Community) included a provision for establishing a Common Agricultural Policy (by the use of state protectionism) to provide for a stable basis for the Community foodstuffs security. In a short time, however, the policy led to big surpluses of foodstuffs production, which was due to unimaginative minds of politicians on efficiency growth in farming, the effect being a big cost of the Policy, hindering development of the Union in its present shape.

Now the most important war, though fought with no armies, but by the use of monopolies and with participation of politicians, is the war about energy supply security. It is a war fought at the expense of societies and natural environment. However, the situation in agriculture and power industry can soon change radically, when man will be using land to produce energy [2, 3]. Then surplus in production of foodstuffs and deficit of energy will stop (separately) being a nice area of practicing politics. And competition in agriculture, power industry and the environment will lead to historical allocation of resources.

Jan Popczyk / Silesian University of Technology

TPA principle – USA, Europe)4. Technological isolationism is more dangerous – it means no capacity for opening to technological universalisation. The universalisation, with global technological development as its starting point, began on a large scale in the 1990s (the Internet, acceleration in biotechnology, microprocessor, gas production, combi and cogeneration technologies, mass application of heat pumps, commercialisation of hybrid/electric car, reaching construction maturity of hydrogen car, as well as acceleration of work on hydrogen airplane). The analogies in the current power sector situation in the world to the events that shook American electric power industry in the 1960s and 1970 are already very clear. Concrete facts can be pointed out to in individual areas, namely: • Liquid fuels: stock market prices of crude oil, which in mid 2008 reached the level of 150 USD/barrel, and no drilling capacity (unlike during the first oil crisis of 1973–1974, when there was a capacity, so the threat was smaller) • Gas industry: the prices of natural gas in bilateral contracts – 500 USD/1000 m3, announced already in 2008 (by Russia) and also no drilling capacity • The environment: strong determination of the European Commission to totally eliminate free of charge CO2 emission allowances and to forecast the European market price of these allowances at minimum of EUR 40 /ton (with complications connected with different than European one American policy of climate change management and no consent of China and India to internalisation of external environmental costs) • Agriculture: totally manipulated media coverage of foodstuffs prices growth in the context of (liquid) biofuels production5, blocking liquidation of the EU Common Agricultural Policy, blocking development of energy agriculture and GMO technologies. All the global threats mentioned above transfer very acutely to Poland, because they are reinforced in individual sectors by very negative conditions, even growing recently. It is of special significance that there is a total lack of a government concept of regulation system (together with support systems), ensuring market coordination of development of wind, biomass, traditional coal, nuclear and clean coal power industry. Special danger is posed by an uncontrollable trend to develop programmes which, if combined, considerably exceed the needs, and on the other hand do not take into account the difficulties involved in further development of networks and potential impact on the change of fuel-power balance of such technologies as electric car and heat pump. The presented wide historical-civilisation context and Polish conditions leaves no doubt: in the decades to come Polish electric power industry will be shifting from industrial society to advanced knowledge society, and then to no-emission/hydrogen one. And the related big tensions are inevitable. The aim is to minimise the losses connected with transformation, and to maximise taking the opportunities (“velvet revolution” would be a good solution).

HOW TO SHEPHERD POLISH ELECTRIC POWER INDUSTRY THROUGH THE TRANSITION PERIOD OF 2008 –2020 AND ENSURE ITS ECONOMIC-ECOLOGICAL EFFICIENCY AND ADEQUACY WITH GLOBAL TRENDS? Market mechanisms in electric power industry can be spoiled, but it is impossible to block them in the longrun. If one admits that it is true, then in production area the answers to the questions asked can be looked for, inter alia, in table 1. That is to say that certain technologies (nuclear, CCT coal) are out of reach in the decade to come. Traditional coal technologies (including supercritical fluid units) can be used but with effects after 20156. Unfortunately, on introducing full charge for CO2 emission allowances and taking into account the actual network charge, these technologies become very expensive, with no scope for competition in long time perspectives. What is left is natural gas cogeneration technologies and renewable technologies (wind and cogeneration biogas). Fuel is essential in gas cogeneration technologies. In this area Poland faces the most difficult transformation, consisting in building a new fuel segment in the form of energy agriculture, of a very big potential in 2020, of 140 TWh in the market of primary fuels (Table 3), and of even bigger potential in the market of final energy, exceeding 100 TWh7. 4 The reforms, mainly the second British successful reform of electric power industry with global effects (1989/1990), would not have been possible if it had not been for many other related reforms, such as: liberalisation of telecommunications in USA – 1982 and British privatisationliberalisation reforms outside electric power industry (in coal mining – 1984/85 and gas industry – 1985), and also the first unsuccessful reform in British electric power industry – 1984. 5 Biofuels cannot cause a significant growth of foodstuffs prices if only 2% of arable land is allocated for energy agriculture and the share of farming products in foodstuffs prices is not more than 20%. It should also be emphasised that second generation biomass fuels can evoke a reverse effect, that is a drop of foodstuffs prices as biofuels can hinder growth of prices of energy and fuels, that is also prices of fertilisers. 6 It does not refer to Łagisza and Bełchatów units (under construction), which will be launched before 2011. 7 Taking into consideration the constraints connected with the required minimum share of renewable energy in the market of transport fuels, of 10% (the target was specified in the European Union 3x20 Energy and Climate Package).

INNOVATIVE POWER INDUSTRY. Ecological-power engineering and economic-civilisation context

A big potential in the form of energy efficient technologies on the demand side is a separate issue from the point of view of Polish national energy security. That is to say that till 2020 it is possible to reduce energy consumption of Polish economy (GDP in fixed prices, from 125 MWh/million PLN (it is worth noting that this energy consumption of economy is matched with the share of electric energy in GDP of almost 4%) to 100 MWh/million PLN, that is by 20%8. Yet another issue is the use of the potential of changing export/import balance from export to import option (change of annual export balance of ca 6 TWh in 2007 to import balance of ca 10 TWh, which is possible already in 2013, especially when 750 kV transmission system is equipped with back to back coupling9). Table 1. Susceptibility of production technologies (together with network investments) and energy efficient technologies to market signals on the demand side Technology Coal (traditional) Nuclear Coal CCT (CCS, IGCC...) Wind Natural Biogas Energy efficient technologies on the demand side

Minimum investment expenditure [in million PLN] Time of response to market signals [years] 2 000 10 000 3 000 10... 1 500 1 10 Practically any funds are useful

8 15 20 2... 5 1 2 from zero1 to more than ten years2

1 Individual (consumer/prosuments) replacement of energy intensive devices with energy efficient ones, existing in the market (replacement of, for example, traditional bulbs with energy saving ones). 2 Transformation of energy intensive economy into energy efficient economy.

The conditions mentioned above (technological, efficiency and system related) will make the next decade a decade of consumers, independent producers and operators in Poland. The role of the latter is emphasised in particular. It means that operators must ensure intensification of the use of the existing networks by innovative activities, rooted in new concepts of heat load capacity of overhead line (treated dynamically), short-circuit strength of facilities, as well as quality of electric energy, supported by statistical-probabilistic model. The research in this area in Poland has a very long tradition in the Faculty of Electrical Engineering of Silesian University of Technology (the first research was done in the 1970s and the 1980s by Jan Popczyk, Kurt Żmuda, Jerzy Macełko, Andrzej Polaczek and Andrzej Błaszczyk, and now by Kurt Żmuda and Edward Siwy). There is a great potential in the area of network use intensification [8, 9, 10]. It refers in particular to electric power networks, which for decades had been optimised by the criteria that the electric energy market verified negatively10. That is to say that the market creates new competitiveness of sources, different from the one that was characteristic for national monopolies. The network developed in the past, of transmission capacities determined by a very conservative system of technical criteria, concerning mainly heat load capacity of the wiring, makes it impossible to use cheap production sources, but it forces operators to use services of expensive producers. On the other hand, tele-information and microprocessor technologies enable change of conservative criteria. That is to say that the technologies enable new approach to management of network transmission capacities. The approach is based on combining heat load capacity of overhead wiring with actual weather condition (wind velocity, air temperature, sun exposure). And progress in materials engineering has provided access to high temperature wires for a long time. Replacing traditional wiring of overhead lines with high temperature ones, which does not happen very often in Poland, is a very effective way of increasing network transmission capacity. Intensified use of existing networks in the second decade can in no circumstances be treated as a beautifying procedure. Apart from the two factors mentioned above (dynamic load capacity and high temperature wires), the real great potential also has a third pillar. That is to say that in monopolistic electric power industry networks were adapted to sources. It was due to the dominant position of production sub-sector (with big production units), formed in a long historical process. In electric power market, at the stage of competition created according to TPA principle, there comes a time for reversing the order. Adapting sources to existing network becomes a very strong 8 The potential for real reduction of electric energy consumption is probably much bigger, which can be seen in particular in the data coming from USA [7]. 9 In reality, there is much more to the problem than just a technical-economic dimension. It also has a political dimension, with which a big business risk of possible project implementation is connected. 10 Moreover, electric power networks, in particular in Poland, did not enjoy the progress in the area of operation (in the area of diagnosis of devices, work under voltage, management of liquidation of effects of big failures).

Jan Popczyk / Silesian University of Technology

principle which enables solving many practical problems, impossible to solve under the old order. Weak rural networks (low and medium voltage) are one of the important examples in this respect. In the old order the solution would have to consist in classical (network) re-electrification of Polish rural areas. Modern market solution consists in re-electrification based on innovative, scattered and production power industry as well as on energy agriculture (based on the rural areas’ own resources). Intensification of the use of existing networks means an urgent need to build a public (for market entities) map of available network resources. In particular, this map should be a carrier of a new system of locational signals, based on node prices. In the decade to come, the system should be addressed to: • end users (industrial investors interested in buying cheap electric energy in the areas of surplus of network flow capacities in particular) • system services suppliers (interested in e.g. construction of intervention sources, reserve sources for wind power industry, etc.) • producers in large scale power industry (interested in modernisation of the existing units) • investors in the area of scattered power industry (interested in construction of local sources in the areas of high level of electric energy prices and deficit of network transmission capacity).

FROM SCATTERING TO THE SYSTEM AND BACK By its nature, electric power industry was scattered at the beginning (the end of 19th century). However, at the stage of general electrification of individual countries the way of its functioning became a serious limitation in reducing costs of electric energy production. That is why serious changes in functioning of electric power industry must have taken place in the further development process. The changes went towards combining small systems into bigger and bigger ones by the use of network. But as long as production units were not too big (till mid 20th century), the pressure on increasing the systems was not big either, and the size of the systems was limited (they did not cross the borders of regions in individual countries). Big combined systems (crossing borders of countries) have been characteristic for electric power industry since mid 20th century. The reason why the systems developed was aiming at reducing costs of electric energy production, mainly by increasing the power of production units (of the nuclear ones to the level of 1500 MW, coal ones to the level of 800 MW) and selecting the cheapest (at investment and operation stage) set of those bigger units, taking into consideration very strong burden to the consumers. Cost reduction, the care of electric power industry at each stage of its development, is different in monopolistic electric power industry than it is in the market (competitive) one. The essence of optimisation calculation in monopolistic and market (competitive) electric power industry is presented below in a more precise way, with focus on network distribution. The optimisation problem, consisting in economic distribution of loads among production sources, called monopolistic optimisation problem (ERO – energy reduction optimisation), was the most representative example of economics of combined production-transmission systems in subsequent Zadanie ERO polega ogólnie na minimalizacji funkcji: decades (since the 1950s till the 1980s). The problem is also a starting point for modern analysis of node marginal costs in network systems in electric power market, with competition created based on TPA principle. nG Generally speaking, ERO consists in minimisation of the function: Zadanie ERO polega ogólnie minimalizacji funkcji: K (Pna (1) G )  ki  PGi  i 1 nG

K (P PGi  (1) we gdzie: K(PG) jest całkowitym zmiennym wytwarzania energii (1) elektrycznej G )  ki kosztem i 1 wszystkich źródłach pracujących w systemie elektroenergetycznym, ki(PGi) jest nieliniową charakterystyką/funkcją określającą zmienny koszt wytwarzania energii elektrycznej w źródle where: gdzie: K(PG) is K(P a total floating cost of electric energy production in all sources working inelektrycznej electric energy wytwarzania energii we G) jest i, PGi określa moc całkowitym generowaną zmiennym przez źródłokosztem i, natomiast nG jest liczbą źródeł wytwórczych system, ki(PGiwszystkich ) is a non-linear characteristics/function defining floating cost of electric energy production in source źródłach pracujących w systemie elektroenergetycznym, k (P ) jest nieliniową i Gi pracujących w systemie. W zadaniu ERO zakłada się, że znany jest skład jednostek generated by sourceokreślającą i, and nG is zmienny the number of production sources working in the system. In i, PGi defines power charakterystyką/funkcją wytwarzania energii w źródle wytwórczych. Obliczenia wykonuje się dla koszt ustalonej konfiguracji siecielektrycznej przy założeniu stałej ERO it is assumed that composition of production units is known. Calculations are made for a set configuration of mocwgenerowaną przezwęzłach. źródło i, natomiast nG jest liczbą źródeł wytwórczych i,mocy PGi określa odbieranej poszczególnych network, withpracujących the assumption constant power receivedERO in individual nodes. w ofsystemie. W zadaniu zakłada się, że znany jest skład jednostek Jeśli pominąć straty przesyłowe, a także ograniczenia wytwarzania mocy w źródłach If we neglect transmission losses and limitations of power production in sources and przy network constraints, wytwórczych. Obliczenia wykonuje się dla ustalonej konfiguracji sieci założeniu stałej oraz ograniczenia sieciowe, to zadanie minimalizacji funkcji (1) jest zadaniem z power jednym then the problem of function minimisation (1) is a problem with one equivalent limitation, resulting from mocy odbieranej w poszczególnych węzłach. ograniczeniem równościowym, wynikającym z bilansu mocy w połączonym systemie balance in combined electric energy system described with the following equation: Jeśli pominąć straty przesyłowe, a także ograniczenia wytwarzania mocy w źródłach elektroenergetycznym określonym równaniem: oraz ograniczenia sieciowe, to zadanie minimalizacji funkcji (1) jest zadaniem z jednym nw ograniczeniem równościowym,nGwynikającym z bilansu mocy w połączonym systemie (2) P  P  0 (2)   Gi Li elektroenergetycznym określonym równaniem: i 1 nG

i 1 nw

PGi   PLiw  0 i, a nw oznacza liczbę węzłów w (2)sieci. gdzie PLi oznacza moc czynną odbieraną węźle  i 1 i 1 Zadanie to można rozwiązać analitycznie, wykorzystując w tym celu odpowiednio utworzoną funkcję Lagrange’a.

INNOVATIVE POWER INDUSTRY. Ecological-power engineering and economic-civilisation context

where PLi means active power received in node i, and nw means the number of nodes in the network. The problem can be solved analytically, by the use of specially created Lagrange function. In reality, apart from the equivalent constraint (2), supplemented by power losses in the network, the function minimisation problem has three types of non-equivalent constraints. They are: upper and lower limitations of power of production sources, upper limitations of line flowing capacity (current limitations or other branch limitations of the line and transformers) and upper and lower constraints of voltages in nodes of electric energy network (voltage or other node limitations). Kuhn-Tucker theorem is used to solve the problem of non-equivalent limitations (by the use of iterative method). From the economic point of view, characteristics/functions defining floating costs of electric energy production in individual production sources are of fundamental significance in function minimisation problem (1). In practice, in the past, the costs were usually defined for each source, based on its technical efficiency characteristics, set by measurement, and average unit price of fuel. Even more often, cost minimisation in equation (1) was replaced with minimisation of the fuel used. And using average costs in optimisation calculation was a general rule in monopolistic electric power industry. But it must be remembered that competitive market functions based on marginal costs. According to the classical definition, short run marginal cost (SRMC) in node i, called locational marginal price – LMP hereinafter, equals minimum change of total floating cost of energy production in the system, caused by change of demand in that node. In the conditions of Polish electric energy market, the term “short run” is usuK (PG ) ally understood as a period of one hour. That is iwhy constant active power can be a measure of energy received/ LMP SRMC (3) i  P  generated in a node i in a given hour. The definition of short run marginal cost can thus be presented in the folLi lowing way: Krótkookresowy koszt krańcowy energii elektrycznej (krótkookresowa cena węzłowa) K (P ) powinien zostać wyznaczony optymalnym LMPwi  SRMCi  stanieG pracy systemu elektroenergetycznego. (3) W (3) P  celu określenia wartości krótkookresowych kosztów węzłowych należy rozwiązać zadanie Li optymalizacji rozpływu mocy OPF, minimalizujące funkcję celu (1). Po raz pierwszy w literaturze światowej koszt związek między energii optymalnym rozpływem mocy a krótkookresowymi Krótkookresowy krańcowy elektrycznej (krótkookresowa cena węzłowa) Short run marginal cost (locational marginal price) of electric energy should be set in optimum work conkosztamizostać krańcowymi energii elektrycznej stanie w węzłach opisali M.C. Caramanis, R.E. powinien wyznaczony w optymalnym pracy sieci systemu elektroenergetycznego. W ditions of electric energy system. To set the value of short run marginal costs one should solve the problem of Bohn, F.C. Schweppe Spot Pricing: Practice and Theory, IEEE Transactions on celu określenia wartości(Optimal krótkookresowych kosztów węzłowych należy rozwiązać zadanie optimisation of power flow (OPF), minimising target function (1). M.C. Caramanis, R.E. Bohn, F.C. Schweppe (OpPower Apparatus and Systems, 1982).minimalizujące funkcję celu (1). Po raz pierwszy w optymalizacji rozpływu mocy OPF, timal Spot Pricing: Practice and Theory, IEEE Transactions on Power Apparatus and Systems, 1982) were the first Wymienieni przedstawili koncepcję rozpływem zróżnicowanej czasowo i przestrzennie literaturze światowejautorzy związek między optymalnym mocy a krótkookresowymi to describe the relation between optimum power flow and short run marginal costs of electric energy in nodes. węzłowejkrańcowymi ceny energii energii elektrycznej nazwanej price sieci of electricity. W późniejszym kosztami elektrycznej w spot węzłach opisali M.C. Caramanis,okresie R.E. The authors mentioned above presented a concept of diversified in terms of time and space node price of za granicą tematyka ta(Optimal została Spot znacznie rozwinięta w and wieluTheory, opracowaniach, zaś w Polsce Bohn, F.C. Schweppe Pricing: Practice IEEE Transactions on electric energy called spot price of electricity. The problem was later developed in many international publications, m.in. w pracach and prowadzonych na Wydziale Elektrycznym Politechniki Śląskiej (najpierw H. Power Apparatus Systems, 1982). and in Poland in, inter alia, the research carried out in the Faculty of Electrical Engineering of Silesian University Kocot, następnie R. Korab). Zastosowanie zadaniazróżnicowanej OPF na rynkuczasowo energii, ifunkcjonującym Wymienieni autorzy przedstawili koncepcję przestrzennie of Technology (first - H. Kocot, and then - R. Korab). Application of OPF problem in energy market, functioning acwedług modelu aktualnie obowiązującego w spot Polsce, wymaga modyfikacji funkcji celu (1) do węzłowej ceny energii elektrycznej nazwanej price of electricity. W późniejszym okresie cording to the model currently binding in Poland, requires modification of the target function (1) to the following zapostaci: granicą tematyka ta została znacznie rozwinięta w wielu opracowaniach, zaś w Polsce form: m.in. w pracach prowadzonych na Wydziale Elektrycznym Politechniki Śląskiej (najpierw H. nG mn Kocot, następnie R. Korab). Zastosowanie zadaniam OPF na rynku energii, funkcjonującym o KCZaktualnie (PGp , PGrobowiązującego )  CipwPGip  wymaga Cir (PGir  PGir ) (4) według modelu Polsce, modyfikacji funkcji (4) celu (1) do i1 pm1 r 1 postaci:

PGr)of satisfying – ncałkowity kosztin melectric pokrycia zapotrzebowania w systemie Gp, cost mthe n demand G where:gdzie: KCZ(PGp,KCZ(P PGr) – total energy system, PGip – accepted for proo – zaakceptowana do produkcji moc z pasma p oferty przyrostowej elektroenergetycznym, P    KCZ ( P , P ) C P C ( P P ) Gip    Gp Gr ip Gip ir Gir Gir duction power from band p of the growth offer of production unit i, PGp = [PGip; i = 1, 2,..., nG; p = m+1,...,(4) m+n], o i1 pm1 r 1 P = [P ; i = 1, 2,..., n ; p = m+1,..., m+n], – moc oferowana jednostki wytwórczej i, P Gp Gip G G ir o – power offered under band r of the reduction offer of production unit i, PGir – accepted for production power PGir w ramach pasma r oferty redukcyjnej jednostki wytwórczej i, PGir – zaakceptowana do from band rgdzie: of the reduction offerPof unit i, PGrkoszt = [PGir;pokrycia i = 1, 2,..., zapotrzebowania nG; r = 1, 2,..., m], Cipw, Cir systemie – respec– całkowity KCZ(P Gr)production produkcji mocGpz, pasma r oferty redukcyjnej jednostki wytwórczej i, PGr = [PGir; i = 1, 2,..., nG; tively, unit price of energy in band p or r – ofzaakceptowana the growth/reduction of offer moc production unitp i,oferty m, n –przyrostowej respectively, elektroenergetycznym, do produkcji z pasma r = 1, 2,..., m], Cip, CirPGip – odpowiednio jednostkowa cena energii w paśmie p lub r oferty o the numberjednostki of bands ofwytwórczej the reduction/growth offer declared by production unit i. = [PGip; i =wytwórczej 1, 2,..., nG; i,p m, = m+1,..., m+n], P – mocpasm oferowana i, PGp jednostki przyrostowej/redukcyjnej n – odpowiednio oferty Girliczba In market conditions, the variable decisions subject for optimisation in OPF problem consist in power volprzez jednostkę wytwórczą wredukcyjnej/przyrostowej ramach pasma r ofertyzadeklarowanych redukcyjnej jednostki wytwórczej i, PGir –i. zaakceptowana do umes declared by individual production units in bands of balance offers, and the prices offered in those bands are produkcji moc z pasma r oferty redukcyjnej jednostki wytwórczej i, PGr = [PGir; i w = 1,warunkach 2,..., nG; Zmiennymi decyzyjnymi optymalizacji w zadaniu the parameters of the problem. The compositionpodlegającymi of production units is not changed as a resultOPF of calculations. The rrynkowych = 1, 2,..., m], C , C – odpowiednio jednostkowa cena energii w paśmie p lub r oferty ip ir mocy deklarowane jednostki wytwórcze w pasmach solution of the problem issątowielkości be the minimum function (4) przez in the poszczególne area of determined by technical equivalent and przyrostowej/redukcyjnej jednostki wytwórczejw i,tych m, pasmach n – odpowiednio liczba zadania. pasm oferty ofert bilansujących, natomiast ceny oferowane są parametrami Skład non-equivalent limitations. redukcyjnej/przyrostowej zadeklarowanych jednostkę wytwórczą i. wytwórczych ulega (4) zmianie wprzez wyniku przeprowadzenia Takingjednostek into consideration targetnie function and classical definition of short runobliczeń. marginal W costzadaniu (3), in tym the się energy minimum funkcji (4)define w obszarze techniczne ograniczenia Zmiennymi decyzyjnymi w przez zadaniu warunkach conditions ofposzukuje Polish electric market, onepodlegającymi can shortoptymalizacji runokreślonym marginal cost in node iOPF in the w following way: równościowe i nierównościowe. rynkowych są wielkości mocy deklarowane przez poszczególne jednostki wytwórcze w pasmach ofert bilansujących, natomiast tych pasmach są parametrami zadania. Skład Uwzględniając funkcjęceny celuoferowane (4) oraz wklasyczną definicję krótkookresowego kosztu jednostek wytwórczych nie ulega zmianie w wyniku przeprowadzenia obliczeń. W zadaniu tym

jednostek wytwórczych nie ulega zmianie w wyniku przeprowadzenia obliczeń. W zadaniu tym poszukuje się minimum funkcji (4) w obszarze określonym przez techniczne ograniczenia równościowe i nierównościowe.

Jan Popczyk / Silesian University of Technology

Uwzględniając funkcję celu (4) oraz klasyczną definicję krótkookresowego kosztu krańcowego (3), w warunkach polskiego rynku energii elektrycznej, krótkookresowy koszt krańcowy w węźle i można zdefiniować następująco: KCZ (PGp , PGr ) LMPi SRMCi  PLi

(5)

Short runKrótkookresowy node cost (5) can koszt be splitwęzłowy into components of simple physical interpretation, that interpretacji is: node cost of (5) można rozłożyć na gałęziowych/prądowych składniki o prostej strat sieciowych (od przepływu mocycost pozornych), koszt ograniczeń i electric energy, active in balancing node, of network losses (apparent power flows), cost of branch/current fizykalnej, węzłowych/napięciowych. są to: koszt węzłowy energii elektrycznej, czynnej w węźle bilansującym, koszt koszt ograniczeń W formie analitycznej składniki te mają postać: limitations and cost of node/voltage limitations. In their analytical form, the components are as follows:

 P LMPi 1  str PLi 

ng nw S U j  Q  LMPb  str LMPqb   µ gmax g     µUjmin  µUjmax  PLi PLi j 1 PLi g 1 

(6) (6)

gdzie: LMP energii biernejinwbalancing węźle bilansującym, , Qstr of active b, LMP qb ––cena where: LMP , LMP nodewęzłowa price of active andczynnej reactivei energy node, Pstr, Qstr –Pstr losses b qb straty mocy i biernejS w sieci, Sg power – przepływ w gałęzi g, Uinj –node moduł and– reactive powerczynnej in the network, – apparent flow inmocy branchpozornej g, Uj – voltage module j, m – vector g napięcia w węźle j, µ – wektor mnożników Kuhna–Tuckera dla ograniczeń of Kuhn–Tucker multipliers for non-equivalent limitations, ng – number of branches. gałęzi. very strong locational signals and significantly enhance competition nierównościowych, ng – liczbaconstitute Short run node costs/prices conditions in combined systems. In practice it means, inter alia, transfer to lower voltage Krótkookresowe koszty/ceny węzłowe stanowią bardzo silneof production sygnały lokalizacyjne i levels, close to consumers. It should be noted, however, that the competition concept according to TPA principle and znacznie polepszają uwarunkowania dla konkurencji w połączonych systemach. W praktyce development the methodology of node costs/prices) in the world coincided with rapid development oznacza toofmiędzy innymi przenoszenie wytwarzania na niższe poziomy napięciowe, bliżejof cogeneration gas technologies (natural gas), due to which the trend of transferring production closer to consumers odbiorców. Trzeba przy tym podkreślić, że koncepcja konkurencji według zasady TPA i (including heat consumers) has strengthened considerably (the California crisis in the period of 2000–2001, rozwój metodyki kosztów/cen węzłowych) na świecie zbiegły się w czasie z gwałtownym which could have beengazowych effectively technologii developed by kogeneracyjnych the use of a shock growth of gas cogeneration, considerably contributed rozwojem (na gaz ziemny). Dzięki temu trend to that trend). wytwarzania bliżej odbiorców (u których są odbiory ciepła) niezwykle się przenoszenia Now the(kryzys processkalifornijski of transferring closer to który consumers entering its second phase, caused by wzmocnił w production latach 2000–2001, możnais było rozwiązać efektywnie 11 political decisions on the use of renewable energygazowej, , which,znacznie by its nature, is tego scattered. Development of applicaza pomocą szokowego wzrostu kogeneracji się do przyczynił). tions of renewable technologies, seen jointly with the systems of their technical control and market management, proces przenoszenia bliżej odbiorców wchodzi w drugąunits, fazę,big a network clearly Obecnie leads to qualitative changes. That wytwarzania is to say that economic effect of scale (big production 11 powodują ją decyzje dotyczące wykorzystania energetyki the odnawialnej , któraatzthe comsystems) is replaced with apolityczne stronger effect of local technological integration, examples being, natury jest rozproszona. Rozwój zastosowań technologii odnawialnych, widzianych łącznie z mercial level, wind farms integrated with the existing pumped-storage power plants, biogas plants integrated with systemami ich sterowania technicznego i zarządzania rynkowego, w sposób widoczny cogeneration sources and local gas systems (natural gas), as well as with local liquid biofuel plants (now transport prowadzi do nowych zmian (pellets, jakościowych. Mianowicie, ekonomiczny efekt skali (wielkie ones) and enhanced solid biofuels briquettes) and many other. bloki wytwórcze, systemy sieciowe) jest wypierany silniejszy lokalnejgases reDevelopment of wielkie second generation fuels12, mainly gas biofuels przez (second decade) efekt and synthetic integracji technologicznej. Przykładami takiej integracji są już, na poziomie komercyjnym, ceived from coal (hard and brown coal) processing, (third decade) will be the driving force of technical integration farmy wiatrowe integrowane z istniejącymi szczytowo-pompowymi, in the two decades to come. That development will open upelektrowniami the way for hydrogen power production industry and biogazownie integrowane ze źródłami kogeneracyjnymi i lokalnymi gazowymi universalisation of power technologies, that is for the technologies that may be systemami practically used at all three final (gazu ziemnego), a także z lokalnymi wytwórniami biopaliw płynnych (obecnie markets: of electric energy, heat and transport. Fuel cell will be a symbol of those technologies. The following transportowych) i ulepszonych biopaliw stałych (pelety, brykiety) i wiele innych. are already spectacular examples of hydrogen projects: California – network hydrogen stations (1000 stations in 2014) and fleet of hydrogen buses, Norway – wind-hydrogen island, automobile industry – Toyota, Siłąanapędową integracji technologicznej w kolejnych dwóch dekadach będzie rozwójMercedes, 12 aviation Boeing. , przede wszystkim biopaliw gazowych (druga dekada) i gazów paliwindustry drugiej– generacji Denmark is the most important in Europe, confirming trends in scattered syntezowych otrzymywanych wexample procesie przeróbki węgla,development zarówno kamiennego, jak ipower industry. The American (USA)dekada). experience is of key ten significance, consists in: on the one hand, withdrawal brunatnego (trzecia Rozwój otworzyhowever. drogę Itdo energetyki wodorowej i from large scale technologies, and on the other hand – experience connected with functioning of more uniwersalizacji technologii energetycznych, tzn. do takich technologii, które będą się than ten million autonomous production sources. praktycznie nadawać do wykorzystania na wszystkich trzech rynkach końcowych: energii elektrycznej, ciepła i transportu. Symbolem tych technologii będzie ogniwo paliwowe. EVOLUTION OF ECONOMICS POWER wodorowych INDUSTRY. INTERNALISATION OF EXTERNAL ENVIRONSpektakularnymi przykładamiINprojektów już obecnie są: Kalifornia – sieć stacji MENTAL COSTS(1000 – NEW STRUCTURE OF iEXCISE – NEW STRUCTURE COMPETITIVENESS OF wodorowych stacji w 2014 roku) flota autobusów wodorowych,OF Norwegia – wyspa POWER TECHNOLOGIES wiatrowo-wodorowa, przemysł samochodowy – Toyota, Mercedes, lotnictwo – Boeing. Assessment of investment in monopolisticsiłę cost economics. In this case the Najważniejszym przykładem effectiveness w Europie, potwierdzającym trendów rozwojowych scope of investments in production results from the necessityznaczenie to maximally satisfydoświadczenia the demand for electric energetyki rozproszonej, jestsources Dania. Jednak kluczowe mają energy, taking into consideration the normative reserve margin. And the optimisation methodology consists in amerykańskie (USA). Na te ostatnie doświadczenia składają się: odwrót od technologii 11 In other words, aiming at primary fuels consumption reduction and environmental protection (now CO2 emission reduction). 12 Farmers define second generation fuels as the ones whose production is competitive to foodstuffs production. And power industry people 11 Inaczej, dążenie do (e.g. obniżenia paliw pierwotnych ochrona redukcja emisji CO2). as the ones that have high 1.6) ratiozużycia of process output energy to the ienergy usedśrodowiska in the process(obecnie of receiving fuel. 12

Rolnicy definiują paliwa drugiej generacji jako te, których produkcja nie jest konkurencyjna względem produkcji żywności. Energetycy natomiast jako te, które mają wysoki (np. 1,6) stosunek energii na wyjściu z procesu do energii włożonej w procesie pozyskiwania paliwa.

energetycznych energetycznych Ewolucja ekonomiki w energetyce. kosztówekonomice zewnętrznych środowiska Ocena efektywności inwestycji Internalizacja w monopolistycznej kosztowej. W –tym Ocenastruktura efektywności inwestycji w –monopolistycznej ekonomice kosztowej. W tym nowa podatku akcyzowego nowa struktura konkurencyjności technologii przypadku zakres inwestycji w źródła wytwórcze wynika z konieczności pokrycia INNOVATIVE POWER przypadku zakres inwestycji w źródła wytwórcze wynika z INDUSTRY. konieczności pokrycia energetycznych maksymalnego zapotrzebowania na energię elektryczną, z uwzględnieniem normatywnego Ecological-power engineering and economic-civilisation contextnormatywnego maksymalnego zapotrzebowania na energię elektryczną, z uwzględnieniem marginesu rezerwy. Metodyka optymalizacyjna polega zaś na wyborze wariantu Ocena efektywności monopolistycznej ekonomice W tym marginesu rezerwy. inwestycji Metodyka w optymalizacyjna polega zaś na kosztowej. wyborze wariantu inwestycyjnego, zapewniającego jego minimalny koszt łącznyz (budowy i eksploatacji) przypadku zakres inwestycji w źródła wytwórcze wynika konieczności pokrycia inwestycyjnego, zapewniającego jego for minimalny koszt łączny (budowy i and eksploatacji) selecting such an investmentzapotrzebowania variant would provide itselektryczną, minimum total (of construction operation) zdyskontowany na rokthat zerowy: maksymalnego na energię z cost uwzględnieniem normatywnego zdyskontowany na rok zerowy: discounted marginesu to zero year: rezerwy. Metodyka optymalizacyjna polega zaś na wyborze wariantu inwestycyjnego, zapewniającego jego minimalny koszt łączny (budowy i eksploatacji) T T zdyskontowany na rok zerowy: ( J  K ) a  min (7)  ( J tt  Ktt) att  min (7) (7)  t 0 t 0

 t 0

1 at  1 t t ( J tatKt1)art  1  r  min

(8) (8) (7)

1 eksploatacji, a – współczynnik dyskontujący, r – gdzie: J – nakłady inwestycyjne, Kt –koszty (8) r – t gdzie: J – nakłady inwestycyjne, a K – koszty eksploatacji, a – współczynnik dyskontujący,  r  lata w okresie życia projektu. (8) stopa dyskonta, t – indeks oznaczający1kolejne stopa dyskonta, t – indeks oznaczający kolejne lata w okresie życia projektu. Odmianą zadania jest zadanie polegające na zastąpieniu normatywnego odwzorowania Odmianą zadania jest zadanie na zastąpieniu normatywnego odwzorowania gdzie: J – nakłady inwestycyjne, Kw – polegające koszty eksploatacji, a – współczynnik dyskontujący, r– odwzorowaniem kosztu zawodności. where:niezawodności J – investment expenditure, K – costs ofpostaci operation, a – discounting ratio, Wówczas r – discount minimalizacji rate, t – index niezawodności odwzorowaniem w postaci kosztu zawodności. Wówczas minimalizacji stopa dyskonta, t – indeks oznaczający kolejne lata w okresie życia projektu. podlega zdyskontowany koszt obejmujący trzy składniki: nakłady inwestycyjne, koszty specifying subsequent years during the project podlega zdyskontowany koszt lifetime. obejmujący trzy składniki: nakłady inwestycyjne, koszty eksploatacyjne i inodrębnie określone koszty zawodności. Koszty zawodności określa się dla The problem consisting replacing normative mapping of withnormatywnego a mapping in theodwzorowania form of cost of Odmianą zadania jest zadanie nareliability zastąpieniu eksploatacyjne i odrębnie określonepolegające koszty zawodności. Koszty zawodności określa się dla zróżnicowanych wariantów inwestycyjnych, przy tym takich, które przynajmniej w unreliabilityniezawodności is a variant of theodwzorowaniem problem. Then discounted costkosztu including three components: expendiw postaci minimalizacji zróżnicowanych wariantów inwestycyjnych, przy zawodności. tym takich, Wówczas któreinvestment przynajmniej w warunkach normalnych zapewniają pokrycie maksymalnego zapotrzebowania. ture, cost ofpodlega operationzdyskontowany and separately determined costs of unreliability are subject for minimisation. Costs of unrekoszt obejmujący trzy składniki: nakłady inwestycyjne, koszty warunkach normalnych zapewniają pokrycie maksymalnego zapotrzebowania. liability are eksploatacyjne determined for various investment variants, that is the ones which at least in normal conditions ensure i odrębnie określone koszty zawodności. Koszty zawodności określa się dla Oczywiście, konsekwencją przedstawionej tu ekonomiki są wynikowe ceny, Oczywiście, konsekwencją przedstawionej tu ekonomiki są wynikowe ceny, satisfying maximum demand. zróżnicowanych wariantów inwestycyjnych, przy tym ale takich, które przynajmniej przenoszące łączny koszt, wprawdzie zminimalizowany, uniemożliwiający odbiorcomw i odbiorcom przenoszące łączny koszt, wprawdzie zminimalizowany, ale uniemożliwiający Of course, the consequences of the economics presented here are resultant prices, transferring the totali warunkach normalnych zapewniają pokrycie maksymalnego zapotrzebowania. dostawcom podjęcie gry popytowo-podażowej. dostawcom podjęcie gry popytowo-podażowej. cost, minimised as it is but making it impossible for consumers and suppliers to take up a demand-supply game. Oczywiście, konsekwencją przedstawionej ekonomice tu ekonomiki są wynikowe ceny, Ocena efektywności inwestycji w konkurencyjnej rynkowej. W tym przypadku Ocena efektywności inwestycji w konkurencyjnej ekonomice rynkowej. W tym przypadku odbiorcom i przenoszące łączny koszt, wprawdzie zminimalizowany, ale uniemożliwiający następuje odwrócenie sytuacji. Inwestor bada rynek, w szczególności określa cenę, jaką może Assessment investment effectiveness competitive market economics. In this case the następujeofodwrócenie sytuacji. Inwestorin bada rynek, w szczególności określa cenę, jaką może dostawcom podjęcie gry popytowo-podażowej. uzyskać za towar/usługę (prognozuje cenę, którą zapłaci odbiorca). Przyjmując tę cenę za situation is reversed. investor researches the market, in particular he determines thePrzyjmując price that hetę cancenę get for uzyskać The za towar/usługę (prognozuje cenę, którą zapłaci odbiorca). za punkt wyjścia, dokonuje ocenyw konkurencyjnej efektywności inwestycji i price podejmuje pozytywną decyzję Ocena inwestycji ekonomice rynkowej. W tym przypadku the commodity/service (he forecasts the price consumer will pay). Adopting as a starting point, hedecyzję makes punkt efektywności wyjścia, dokonuje ocenythe efektywności inwestycji i podejmuje pozytywną inwestycyjną tylko wówczas, jeśli wskaźniki efektywności są dla niego satysfakcjonujące pod następuje odwrócenie sytuacji. Inwestor bada rynek, w szczególności określa cenę, jaką może an assessment of investment effectiveness and makes a positive investment decision only if effectiveness indicainwestycyjną tylko wówczas, jeśli wskaźniki efektywności są dla niego satysfakcjonujące pod względem oczekiwanego wynagrodzenia i zaangażowanego kapitału własnego (nie może za expected towar/usługę (prognozuje cenę, zapłaci (he odbiorca). Przyjmując tę(nie cenę zain tors satisfy uzyskać him for the remuneration and own capital employed cannot get better remuneration względem oczekiwanego wynagrodzenia i którą zaangażowanego kapitału własnego może uzyskać lepszego wynagrodzenia na otwartym rynku kapitałowym). punkt wyjścia, dokonuje oceny efektywności inwestycji i podejmuje pozytywną decyzję open capitaluzyskać market).lepszego wynagrodzenia na otwartym rynku kapitałowym). inwestycyjną tylko wówczas, jeśli wskaźniki efektywności są dla niego satysfakcjonujące pod względem oczekiwanego wynagrodzenia i zaangażowanego kapitału własnego (nie może T T T T uzyskać lepszego wynagrodzenia naCF otwartym NPV   a rynku a CFkapitałowym).  J (9) (9) NPV   a t CFtt  a t CFtt  J oo (9) t 0 t t 1 t t 0

t 1

kosztach a także ryzyk. W analizie ekonomiczno-finansowej where: CF – accumulated cash flow, IRR r, IRR – internal rate of return for>which NPV = uwzględnienie 0. gdzie: CFkredytów), – skumulowany przepływ finansowy (cash IRR r, IRR –(9) wewnętrzna stopa NPV przepływ a>t CF  at(cash CF flow), J o IRR (9)stopa   t t flow), gdzie: CF – skumulowany finansowy > r, IRR – wewnętrzna kredytów staje się podstawowym wymaganiem metodologicznym. Therepodatków, is one more fundamental effectiveness assessments (7) and (9). That is to say zwrotu, dlakosztów której NPV =difference 0. t i 0ryzykbetween t 1 zwrotu, dla której NPV = 0. that economic analysis (7), based on discount rates, does not take into consideration tax rates and interest rates Istnieje jeszcze jedna fundamentalna różnica między ocenami efektywności (7) i (9). UwagiIstnieje dotyczące analizy Problemróżnica stopy dyskontowej. Formalne metody(7) analizy jeszcze jednaryzyka. fundamentalna między ocenami efektywności i (9). (bank interest rates that decide about costs of credit), and risks. In economic-financial analysis (9), taking into Mianowicie, w analizie ekonomicznej (7), której podstawą są stopy dyskontowe, nie gdzie: CF – skumulowany przepływ finansowy (cash flow), IRR > r, IRR – wewnętrzna stopa ryzyka inwestycyjnego obszarze inwestycji materialnych), do zastosowań Mianowicie, w analizie(wekonomicznej (7), której podstawą nadające są stopysiędyskontowe, nie consideration taxes, costs of credit and risks become a fundamental methodological requirement. uwzględnia się stóp podatkowych i stóp procentowych (stóp bankowych decydujących zwrotu, dla której NPV = 0. praktycznych, w elektroenergetyce dopiero w początkowej fazie rozwoju (jest to innaoo uwzględnia sięsąstóp podatkowych i stóp procentowych (stóp bankowych decydujących Istnieje jedna fundamentalna różnica między ocenamiwahań efektywności i (9). sytuacja niż jeszcze w zastosowaniach dotyczących krótkookresowych cen na(7)rynkach Remarks on risk analysis. Theekonomicznej problem ofgdzie discount rate. Thejest formal methods of proste investment risk analysis Mianowicie, w analizie (7), której podstawą są stopy dyskontowe, nie giełdowych energii elektrycznej, możliwe stosunkowo wykorzystanie (in the areauwzględnia of tangible investments) that can be used in practice are at an initial stage of development in electric się stóp podatkowych i stóp procentowych (stóp bankowych decydujących o zaawansowanych metod z rynków finansowych). Jedną z koncepcji, którą można wskazać power industry (it is a situation different from the one in applications concerning short-term fluctuations of prices jako obiecującą, jest budowa modelu statystyczno-probabilistycznego nałożonego na analizę9 9 in electric energy stock markets, where it czyli is possible to use, in a relatively way, advanced methods of finanprzepływów finansowych, analizę, której podstawąsimple jest wzór (9). Punktem wyjścia do cial markets). Development a statistical-probabilistic model imposed flow analysis, that is być the analysis budowy modeluofstatystyczno-probabilistycznego ryzykaonwcash tej koncepcji powinna analiza on which formula (9) is based, seems to be one of the promising concepts. Sensitivity analysis, generally used 9in wrażliwości stosowana powszechnie w praktyce, a ponadto stosowane w ekonomii modele practice, andanalityczne the analytical models of selected macroeconomic elements, used in economics, should constitute the wybranych wielkości makroekonomicznych. starting points in developing statistical-probabilistic model of risk. Jedną najważniejszych makroekonomicznych, w Discount rate is one zof the most important wielkości microeconomic indicators used in cashwykorzystywanych flow analysis. In an anaStopa ta w postaci analitycznej analizie przepływów finansowych, jest stopa dyskontowa. lytical form, discount rate can be presented in the following way: może być wyrażona w sposób następujący: r = 1s a ∗ 1s r  −1

(10)

gdzie: sa – jest kosztem alternatywnym kapitału (najczęściej równym oprocentowaniu państwowych obligacji długoterminowych), sr – jest natomiast stopą ryzyka, charakterystyczną dla danej działalności gospodarczej.

Jan Popczyk / Silesian University of Technology

where: sa – is an alternative cost of capital (usually equal to interest rate on long-term state bonds), sr – is a risk rate, characteristic for the given business. Discount rate characterises the standing of the economy and its stability in long-term investment perspective and in particular constitutes a basis for investment decisions of key significance in sectors of the biggest capital consumption. As a parameter that enables taking into account change of money value in time, discount rate fundamentally affects optimum (for the given economy) structure of investment expenditure (distributed over investment time) and future operation costs (incurred over a long period of time). It is clear that high discount rates, characteristic for weak and instable economies, lead to solutions of low investment expenditure and high operation cost, but low rates – just the opposite – to solutions of high investment costs and low operation costs. If one neglects technological risk and risk of change of fuel prices, then application of discount calculation provides better opportunities for existence of water power plants (and generally, renewable sources of electric energy), and nuclear power plants in USA and Western Europe. And gas power plants (or oil powered ones) are more proper for Africa and South America. Similarly, low discount rate in USA and in the European Union prefers electric power lines of big cross-sections of working cables (of higher investment expenditure, lower costs of power and energy losses), and high discount rate, characteristic for the economies of African and South American countries, leads to smaller cross-sections of working cables of electric power lines. The choice of a discount rate to illustrate the problem of risk in electric power market, and generally in the markets with the required capital consuming infrastructure, is of characteristic significance from many points of view (apart from the point of view connected with calculation technique), of which the following two are the most important ones. Firstly, the approach to discount rate expressed by formula (10) indicates that the market will be forcing similarity of traditional methodologies of economic assessments of material infrastructure investments and the methodologies of assessing capital investments. It means, of course, universalisation and levelling as tendencies, profitability of infrastructure investments and profitability of the market expressed by the use of profitability of stock included in characteristic stock indexes, e.g. American indexes: industrial - Dow Jones Industrial Average, banking - Standard & Poor and technological - Nasdaq. In other words, in competitive markets infrastructure services it means a trend from economic account to financial account and from long-term account to short-term account. Secondly, formula (10) points out to a special task to be performed in terms of the necessary modernisation of regulation systems of infrastructure services markets. That is to say it is necessary for the regulators to develop immediately a basis for setting risk rate sr and determining its reference value, in network infrastructure in particular. In the case of electric power industry, a challenge is posed also by determining risk rate sr, different for individual power technologies, e.g. for nuclear power industry13, for coal, gas, renewable energy industry and for pro-efficient technologies in the area of using electric energy. It is clear that market risk of building a traditional nuclear unit of 1500 MW, for PLN 10 billion differs from the risk of building a unit of 460 MW for PLN 1800 million, powered by hard coal, whose market is shrinking. And it is obvious that the latter is radically different from the risk of building a micro gas powered electric heat plant for PLN 1 million in a fast growing market of cogeneration scattered power industry. And finally, the situation in the market of pro-efficient technologies in the area of using electric energy, where competition mechanisms have been in place for as long time and are stable, is also different.

REFERENCE COSTS/PRICES THAT TAKE INTO ACCOUNT INTERNALISATION OF EXTERNAL COSTS Fig 1 presents reference costs taking into account internalisation of external environmental costs, and also the costs that can soon become a source of stranded costs, that is those of network and system services. A uniform (product) internalisation of CO2 emission costs was adopted in the method used to estimate the presented reference costs. In the light of 3x20 Energy and Climate Package (specifying the total target of CO2 emission reduction in all three final markets: electric energy, heat and transport), this method should surely be improved. The improvement should go towards using the thermo-ecological method connected with egzergy for internalisation of CO2 emission costs. Despite the fact that Fig. 1 presents the change of competitiveness structure of electric energy technologies that seems to be shocking now, one must remember that it is only an introduction to what is going to happen in 13 The risk of nuclear power industry in macroeconomic terms (for example in inflation aspect), that is no longer in terms of big environmental disasters and costs of treatment of used fuel (still, to a great extent, outside the mechanism of internalisation), is becoming a subject of a serious public debate in USA [11].

INNOVATIVE POWER INDUSTRY. Ecological-power engineering and economic-civilisation context

the decades to come. That is to say that the revolution in the area of fuels will cause a decline of the existing excise system and that a new one will be created. The current excise system, developed over decades, is, in particular, subordinated to the way of using fuels. In such a system, diesel fuel used for transport, for example, has a very high excise, but natural gas does not. The same diesel fuel put into a car, having a very high excise, has a much lower excise if it is used in cogeneration aggregate. There are many similar examples. The conclusion is unambiguous - the existing excise, characteristic for industrial society, is totally irrational in knowledge society, and it would be even more irrational in a hydrogen society (now it can by no means be justified for technological reasons, and is even corruptive in this aspect). That is why it is necessary to develop a new, uniform excise system from the scratch. It seems that the thermo-ecological method mentioned above, connected with egzergy, would be even more useful in this case.

Fig. 1. Reference costs for various electric energy technologies and for two values of CO2 emission allowances: 10 euro/ton and 40 euro/ton [8] Technologies: 1 – nuclear unit, transmission network, 2 – brown coal unit, transmission network, 3 – hard coal unit, transmission network, 4 – gas cogeneration source, 110 kV network, 5 – gas cogeneration source, MV network, 6 – gas cogeneration source, LV network, 7 – integrated wind-gas technology, 110 kV network, 8 – biomethane cogeneration source, MV network, 9 – small water power plant, MV network, 10 – fuel cell

Without going into methodological complexities, to illustrate the fact that the new economics changes the competitiveness structure of electric energy technologies, in particular makes large scale coal technologies noncompetitive, it will present, apart from Fig. 1, a simplified estimation of unit cost for Łagisza unit under construction of (supercritical, fluidal) 460 MW. The basic data, deciding about unit cost of electric energy supplied from that unit to end (averaged) user are as follows: investment expenditure – PLN 1.8 billion, net effectiveness – 42%, CO2 emission – 0.8 t/MWh, time of use of nominal power – 7000 h/year. Individual components of unit cost of electric energy for end consumer for the above data are as follows: depreciation (for depreciation period of 30 years) – 20 PLN/MWh, cost of transferable capital (for IRR of 8%) – 60 PLN/MWh, cost of coal – 100 PLN/MWh, cost of CO2 emission allowances – 120 PLN/MWh, fixed costs variabled – 20 PLN/MWh, transfer charge – 100 PLN/MWh. And the total is 420 PLN/MWh. It is a cost very well corresponding with the upper level of the cost for technology 3 (matching Łagisza unit) in Fig. 1.

POWER INDUSTRY SQUEEZED INTO THE MECHANISM OF ECONOMIC CYCLES The year 2009 is very good to start changing the description of future growth of demand for electric energy, from a smooth description not taking into account the changing patterns in economy, to a description strictly correlated with them. The growth of electric energy prices, caused by the growing costs of CO2 emission allowances purchase (and the growth of coal prices), provides an opportunity in this area. It is worth noting that growth of prices is inevitable, which means that it is, to a great extent, beyond effective management. But there is still a certain possibility of managing its effects. The question of how we will use that growth remains open. The key issue, of course, is whether the growth of prices will stimulate investments and development of innovative power industry, or whether the opposite will happen: the growth of prices will be used to finance the growth of operation costs consolidated in the last two years in companies, and to implement old style investments, which will cause big stranded costs in the future.

Jan Popczyk / Silesian University of Technology

If electric energy free market in Poland has a say, then the scenario is easy to envisage. Below are five remarks connected with that scenario. They provide estimates of the impact of growth of prices on macroeconomic indicators, which are only of orientation character (the thing is to describe the problems of supplying economy with electric energy by the use of a new language, characteristic for market approach, and not by the use of the language used so far, the language characteristic for monopolies). The presented estimates should be systematically reviewed and developed (practically speaking, a rigorous methodology providing for more accurate estimates is yet to be developed). 1. A very strong growth of prices of electric energy (of e.g. 50%) immediately translates into growth of consumer inflation (consumer price index – CPI). The potential of that growth is now ca 2%. Short-term inflation translates directly into an increase of interest rates and slow down of economy (decrease of GDP). But with the current, very big power consumption of Polish GDP (125 MWh/million PLN) there is no threat of longterm slow down of economy (bigger than 0.2% annually). 2. Strong growth of prices of electric energy in Poland coincides with a period of weaker economic situation in the world. It means that the cleaning impact of economic cycle on economy, inter alia, reducing its power consumption, in Poland will be bigger than in the countries where there will be no growth of prices of electric energy. It can be assumed that if the correlation coefficient between growth of demand for energy and growth of GDP (in the ascending phase of economic cycle) is now ca 0.5 for Poland, then for the next cycle, the coefficient can be at a very low level of 0.2. 3. It should be remembered here that a strong growth of prices will show the first time ever what price flexibility of demand for electric energy is really like in Poland. The first component of demand decrease, connected with simple economising on electric energy, will reveal, practically speaking, right after the prices grow. The second component, connected with investments to reduce energy consumption of economy (including the planned white certificates), will reveal in ca 2009. The third component, connected with structural changes of economy to more modern one, will reveal in ca 2010. The aggregated annual ratio of decreasing energy consumption in economy (seen as business as usual) should be adopted at the level of ca 1.5% in the perspective to 2020 (such a decrease can be treated as well correlated with the European Union 3x20 Energy and Climate Package). 4. A strong growth of prices will stimulate development of the segment of independent producers. A tangible effect in this area (increased annual supply of electric energy coming from wind and biomethane power industry, of ca 1.5 TWh) is possible after 2–3 years. It is necessary, however, to change the regulations, from consumer oriented regulations to investors and technologies oriented regulations (regulations based on reference costs for individual technologies). 5. The large scale coal electric power industry, even the one in the form of traditional technologies, with effects possible not earlier than after 201514, is not able to respond to the current growth of prices, regardless of how big it will be. It must be emphasised, however, that in the case of traditional coal technologies, it is rather coal, shortages of which will appear, than power that is going to be a problem. And the situation in coal mining industry (in terms of mining investments) is not, in terms of response time to growth of prices, better than in electric power industry (in terms of production and network investments).

INNOVATIVE POWER INDUSTRY – DRIVING FORCE OF ECONOMY AND A BIG AREA OF NEW CONSOLIDATION OF COMPETENCE Although generally accepted in the world, the threat to the climate has not been unambiguously proved. Should it not be then recommended to be moderate in internalising external costs of CO2 emission, in particular in relation to the aggressive European Union strategy in this area and in the light of the fact the United States have not accepted the Kyoto protocol? On the contrary. The fact that the United States have not accepted the Kyoto protocol can in no circumstances be treated as an argument for the fundamental difference of their climate policy in comparison with the European Union policy. It is known that in the time perspective till 2050 the States want to build a mature hydrogen society, and the Union – a no-emission society. So the long-term target is, practically speaking, the same, and the ways of reaching it for both regions lead, in 2020 time perspective, through renewable power industry (innovative). And that is the essence of the problem. 14 By the use of no-emission coal technologies, the response to the growth of prices of electric energy could appear as late as in 2030.

INNOVATIVE POWER INDUSTRY. Ecological-power engineering and economic-civilisation context

Below is presented an attempt at specifying a uniform fundamental perspective for innovative power industry and the most controversial issues from the point of view of operationalisation of power supply security, i.e. a perspective taking into account wind power industry, biomass power industry, ecological foodstuffs security. It is clear that the big problem of power supply, ecological and foodstuffs security on the one hand and of wind and biomass power technologies on the other hand, considered from the point of view natural resources, requires research. But it should be remembered that fossil fuels (created over millions of years), wind, foodstuffs and biomass have the same source – the sun. The author of this article admits that justified is the hypothesis that (at the current technological stage) biomass is, fundamentally speaking, more useful than wind in the chain of solar energy processing into final energy that man needs (electric energy, heat, transport fuels). Furthermore, justified is also the thesis that energy agriculture does not violate foodstuffs security. Such a hypothesis is based on the fact that foodstuffs takes only 1% of biomass growth in the entire biomass balance of the Earth (it is already known that the potential of secure development of energy agriculture has not been exhausted yet, and there already appear energy forests that open a new perspective for second generation biomass fuels). The presented fundamental perspective needs to be supplemented by further factors reinforcing the trend in the form of scattered innovative power industry. The following are the two important factors: the effect of “factory production” and the effect of an “intelligent object”. The first one refers to investment and construction, the other one to operation and operation management (in the future – to operation handling). Replacing power plant construction sites (transformer-distribution stations, electric energy lines) with production of “sources” in factories means replacement of the effect of scale with the effect of series production and is a qualitative change of great potential of innovation. Replacement of traditional operation with servicing of facilities, and traditional operation handling with no service handling in the formula of a virtual power plant and an intelligent object is a similar qualitative change of a great potential of innovation. In subsequent years, energy agriculture can be an area in which there will appear a strong impulse to develop innovative agriculture, energy and ecology related technologies, that is: • environmental biotechnology (waste treatment in municipal economy, in agricultural production, in agricultural products-foodstuffs processing, in industry) • biotechnology of producing biofuels, biomethane, hydrogen from biomass (including cellulose) • tele-information technologies to meet the technical and market needs of networked (virtually scattered) power industry, including virtual power plants. Energy agriculture can also be an impulse for Poland to build modern industry of facilities supply (creating a big demand market for BUMAR industrial group, Cegielski Plant and other companies would serve the purpose well – construction of cogeneration sets, and for Polish shipyards – production of containers for biogas plants). And it should be emphasised that the barrier for entering the mentioned markets of innovative technologies (not all the markets, however) is still relatively low and that it surely can be overcome by Polish science, Polish industry, agriculture, rural areas and power industry. Innovative power industry, which is to be a driving force of economy in the whole world, needs a big educational programme, including a specialist human resources training programme. It is necessary to immediately intensify education to provide economy with specialists in the new professions, such as for example, power auditor (a profession formally developed in Poland in 2008), an engineer for cooperation of scattered sources with network, engineer of intelligent objects, developer of biogas projects (energy-ecological), integrator of infrastructure services in municipalities (professions needed, but non-existent from the formal point of view). The list of the professions can be extended. It is important that they are professions for which there is already a big demand in the European Union. It is also important that they are professions of a totally new consolidation of competence. Among Polish technical universities, Silesian University of Technology has one of the best sets of conditions to teach these professions. But there is a need to change the formula of education (and research). One of the possibilities in this respect could consist in launching an inter-faculty school, “intelligent power industry”, grouping many faculties, with the Faculty of Electrical Engineering as the leader. Telecommunications experience is an example to follow in power industry. So far telecommunications has been the most spectacular example of influence of elimination of a monopoly on development of public utility sector and its transformation into one of the most innovative areas of economy, with very strong worldwide competition. The global liberalisation of telecommunications started with the reforms at the beginning of the 1980s in USA, Great Britain and Japan. And comparing American and British reforms is of special significance here. That is to say that in USA the reform consisted in division of the national monopolist AT&T (a private company). In Great

Jan Popczyk / Silesian University of Technology

Britain the reform is implemented by privatisation of the national monopolist, British Telecom, after allowing (in 1982) the company Mercury to enter the market and an attempt at freeing competition by regulation activities in the duo-monopolistic market. For the first time on a global scale, the practice has shown that privatisation of a monopoly without dividing it and then introducing regulations is not an effective way of stimulating competition in monopolistic infrastructure sectors. It is necessary to divide the monopoly, just like in USA. It should be thus assumed that the following became the driving forces of development of competition in telecommunications: 1. Break-up of the American telecommunications giant AT&T (1982) 2. Liberalisation of telecommunications OECD in countries 3. Technological progress (development of computer industry, development of fibre optics networks, development of mobile phone industry, development of the Internet) 4. Development of international companies that need extended internal (corporate) communication. It must be emphasised, however, that without prior development of tele-information technologies (and measurement technologies) it would not have been possible to apply TPA principle in electric power industry. And it must be remembered that the essence of electric energy market functioning in TPA environment consists in: shock shortening of trading cycles, transformation of the market of technological system services (regulation services in particular) in electric energy market, development of the Internet trade, etc.

POLAND TO ATTAIN THE EUROPEAN UNION TARGETS SPECIFIED IN 3X20 ENERGY AND CLIMATE PACKAGE, AND IN PARTICULAR, DEVELOPMENT POTENTIAL OF POLISH ENERGY AGRICULTURE15 - POSSIBILITY15 3x20 Energy and Climate Package is the brightest star that the European Commission is sending Poland. By the use of the Package, Poland can accelerate its civilisation development. But we need to try to reach the star, to take the opportunity. So far, however, the ones that perceive the package as a disaster are the leading group. From corporate-political perspective, the Package means mainly growth of prices of electric energy, caused by charge for CO2, emission allowances, which after 2012 must significantly exceed PLN 20 billion annually for the business to be able to cover external environmental costs, that is the costs that corporate-political business has not been covering so far. The problem looks totally different from the perspective of knowledge society. If electric energy is to become more expensive (the additional PLN 20 billion must be spent by the society/consumers), then there should be some benefits as well: the money should remain in Poland, as much of it as possible, and it should be used to modernise the economy. Table 2 clearly shows that his condition is met by biogas technologies. In the case of those technologies, that is energy agriculture, the money will stay in Poland, and furthermore, it will become a modernisation impulse for Polish rural areas and a restructuring impulse for Polish agriculture (preparations of Polish agriculture to the effects of “putting out” Common Agricultural Policy after 2013 and to absorb second generation fuels received from coal after 2020 will be used). Table. 2. Share of charges paid for electric energy by end consumers (taking into account covering capital costs, fuel costs and other operation costs and total network costs) that will go to international suppliers Technology

Share [%]

Nuclear

Coal CCT (CCS, IGCC...)

Wind

Natural gas

Biogas

However, it must be emphasised here that the chance to use the big potential of Polish energy agriculture can be lost. In mid 2008 the media announced a great success consisting in creation of a Polish-German alliance to block one of the most fundamental solutions included in the draft of the directive on the use of renewable energy (published in January 2008). 15 The analysis does not yet take into account the big impact of heat pump and electric car on transformation of fuel-energy balance of Poland in the next two decades.

INNOVATIVE POWER INDUSTRY. Ecological-power engineering and economic-civilisation context

And the solution is a single European market of green certificates. The simplest analysis to be made indicates that solution proposed in the draft of the directive is in the interest of Poland. And the Polish-German alliance to block this solution is not in the interest of Poland. Table. 3. Comparison of the potential of energy agriculture of Poland and Germany in the aspect of single European market of green certificates [8] Category

Poland

Germany

Population [million]

Surface area [thousand km2]

314

357

18,6

17,3

Arable land necessary to provide for foodstuffs supply [million ha]

ok. 4

ok. 8,6

Potential of energy agriculture (25% of arable land) 20082, pp3 [TWh]

140

120

Energy needs 2008, pp [TWh]

1100

3845

Share of renewable energy sources in final energy market in 2005 [%]

5,8

7,2

The European Union target (2020) [%]

Energy consumption, pp GDP [MWh/1000 euro]

4,8

2,1

Arable land [million ha] 1

With the average grain production of 7 [ton/ha] (France, Holland, Ireland, Germany), in Poland it is now 3.5 [ton/ha]). The potential of energy agriculture was calculated in a conservative way, but with the assumption that equivalent surface area of energy farming is even twice smaller than the actual one and with the current corn energy efficiency of 50 MWh/ha (in the case of half-sugar beets, the potential is 215 TWh for Poland and 200 TWh for Germany, a in the case of GMO corn - ca 550 TWh and ca 500 TWh, respectively). 3 pp – units referring to primary fuels market. 1 2

The data presented in Table 3 clearly though not directly indicate that Polish potential of energy agriculture, estimated very conservatively, is compatible with the European Union target for Poland in terms of the share of renewable energy (in final energy market). And German potential is ca six times smaller than the German target. So the marginal price of green certificates in the European market, depending to a great extent on the imbalance characteristic for Germany, will be high. In such a situation, it will be possible to sell Polish surplus of green certificates for favourable prices. (The surplus of green certificates will come from the sum of renewable energy resources, including also wind, water, etc. It will also result from higher than adopted for the calculations presented in the table energy efficiency per hectare of arable land) Taking that opportunity and not the Polish-German alliance to block such a solution is the Polish raison d’état.

ELECTRIC POWER INDUSTRY IN 2030 (AT THE TURN OF KNOWLEDGE SOCIETY AND HYDROGEN SOCIETY EPOCHS) For an external observer not specialised in electric energy matters, e.g. a driver, Polish electric energy system in 2030 will differ considerably from the situation that we have now. That is to say that such an observer will see mainly 4 500 wind turbines on huge poles (in the north of the country – grouped mainly in big wind farms of 30–100 turbines, in the middle part – of medium size of 10–30 turbines, and in south – small ones). He will not know, however, that it means as much as 9 000 MW of installed power, but only 18 TWh of annually produced electric energy and 900 MW of available power). Such an external observer will see 50 000 micro biogas plants in farms. The plants will be used to treat biodegradable waste and to handle risk management connected with foodstuffs farming (by diversification of plant product merchandise, that is producing also for energy purposes). He will not know, however, that it means over 2 000 MW of electric power installed and ca 2 000 MW of available power, as well as 15 TWh of annual electric energy production and over 50 PJ of heat. The same observer will see 6 000 single biogas plants in rural areas, where energy beets and corn will be grown. He will not know, however, that it means 6 000 MW of installed electric energy and over 5 000 MW of available power and as much as 45 TWh of annual electric energy production and over 250 PJ of heat. Neither an inexperienced observer nor a professional in energy-heat-gas industry will be able to easily tell from a distance whether the cogeneration source integrated with micro biogas plant/biogas plant works parallel to the electric energy system or whether it is autonomous. Similarly, it will not be easy for him to see that very often a micro biogas plant/biogas plant is not integrated with a cogeneration source, and that the biogas it produces (green gas) is transported in the form of LNG or CNG pumped into a natural gas network and transported to

Jan Popczyk / Silesian University of Technology

another place, where heat is received and used co-production. But a financial investor, a biotechnologist and farmers will know almost everything about micro biogas plant/biogas plant market, about biogas gassing processes and economics of energy agriculture. They will also know a lot about electric energy market. A mayor of a rural community, responsible for crisis management and for infrastructure in his area, a businessman operating in the area (owner of an alcohol distillery, of a big dairy, of a big cattle, hog-raising, chicken farm, of a fruit and vegetable processing plant or of a sugar plant closed as a result of sugar industry restructuring after Poland had joined the EU) and a farmer producer group (growing energy beets and corn) will in 2030 continue to invest in the community ecological-energy centre that developed in the last two decades around the biogas plant treating waste biomass, additionally powered with substrates in the form of energy plants silage, of the plants grown in the energy zone of the community. Apart from a biogas plant integrated with a cogeneration source, the centre will include a second generation liquid fuels production plant and a refined solid biomass production plant (pellets and briquettes). In 2030, a professional in energy-heat-gas industry will know about more than ten natural gas cogeneration sources of electric power of ca 50 MW (in the cities of the population of over 100 000), of a few tens of such sources of the power of a few but not more than twenty MW (in the cities of the population of over 50 000) and of a few thousand of sources of the power of up to 1 MW (small scale cogeneration and micro-cogeneration: in small towns and villages, in office buildings, in public utility objects, in SMEs). A professional in electric energy networks that in 2030 will be looking at a overhead network for topology reasons (lines and stations), will see a picture very similar to that of 2008. But he will know that in last two decades there was a great intensification (even 2-fold one) of the use of electric energy lines and stations (as a result of innovative approach to network resources, put into new modernisation technologies connected with the use of high temperature cables, as well as in new concepts of dynamic load capacity of facilities and their life management, supported by statistical-probabilistic models and tele-information technologies). A professional in electric energy power plants that in 2030 will be looking at large scale production sources for locational reasons, will see, practically speaking, a picture very similar to that of 2008. But he will know that in last two decades there was a great modernisation: that is to say that the old coal units will be replaced with new ones of supercritical parameters, of much higher powers and significantly higher efficiencies. A miner-chemist and at the same time a professional in nuclear energy will in 2030 see a few installations of clean coal technologies (in Silesia and in the vicinity of Legnica). The installations will be producing synthetic petrol, synthesis gasses and hydrogen, using heat nuclear reactors. Fuels from coal processing will be distributed to networks of fuel stations, including networks of hydrogen stations, similar to the network built in California. Hybrid cars (able to become emergency sources of electric energy), airplanes, cogeneration sources (small scale ones and micro sources) will be powered at such stations. Gas piston engines, gas turbines, electric machines and fuel cells will be the production-drive technologies. By 2030 the politicians and farmers in the EU will have forgotten that there was a Common Agricultural Policy. By that time farmers-entrepreneurs will have diversified their operations and will have allocated 20% of arable land for energy farming to provide for better management of their market risk. Such an allocation between foodstuffs and energy segment will provide for market balance of foodstuffs and energy prices, which means that the entire economy will benefit. By 2030 also biotechnologists will have won the battle for GMO technologies to be used in energy farming and will be offering hydrogen produced directly from biomass, without the gas phase. In this way, they will be preparing to announce that the epoch of hydrogen society starts. All the investments (small and very big) will in 2030 be financed from the investorsâ&#x20AC;&#x2122; own resources and from stock exchange capital. The investors will not be carrying out a mission, but they will be earning money and implementing good business practices. A visible hand of a regulator (the state) will not be destroying the invisible hand of the market. The corporate-political alliance will not be terrorising the society with loss of energy security. The state will not be maintaining the system of excise in its present form, rooted in the development phase of industrial society. The consumers will in a natural way take the market risk. In the case of power from electric energy system, they will in particular accept electric energy prices (of energy supplied directly by producers or trading companies), which will be changing only a little slower than stock prices in stock exchanges. But electric energy users will also be able to really choose a fuel-technological system of electric energy (from a network, from a hybrid car, fuel cell, from electric energy storage).

INNOVATIVE POWER INDUSTRY. Ecological-power engineering and economic-civilisation context

CONCLUSION Is there a threat that in the future we will have to cope with big electric power industry problems and huge stranded costs, similar to the ones in the past? Is there a threat of a failure due to lack of competition, great development trend, such as for example, decline of development of nuclear power industry in USA due to lack of competition in nuclear technology supply industry in the 1960s and the 1970? No! In knowledge society and then in hydrogen society it will be less and less possible. The competition will force power engineering solutions similar to the ones in transport and telecommunications (electric energy system will be an equivalent of railway transport and wireless telecommunications, and scattered power industry – of road transport and mobile telephone industry). It will provide for a market development balance of power industry (not only electric power industry) in competitive environment for a long time.

LITERATURE 1. Popczyk J., Zarządzanie i ekonomika na rynkach usług infrastrukturalnych (w świetle reprezentatywnych doświadczeń elektroenergetyki), Gliwice, 2006 (na prawach maszynopisu, www.egie.pl). 2. Popczyk J., Polska sytuacja w aspekcie unijnej strategii energetycznej do 2020 roku, Rynek Energii, 2008, nr 3. 3. Müller-Kraenner S., Bezpieczeństwo energetyczne. Nowy pomiar świata. Wydawnictwo „Z naszej strony”, Szczecin, 2009. 4. Hanney A.A., Stady of the Privatisation of the Electricity Supply Industry in England & Wales, EEE Limited, London, 1994. 5. Energy for Tomorrow’s Word – the Realities, the Real Options and the Agenda for Achievement. WEC Commisson, 1993. 6. Hyman L.S., America’s Electric Utilities: Past, Present and Future. Public Utilities Reports, Inc. Arlington, Virginia, 1992. 7. Grunwald M., Wasting Our Watts (We don’t need new drilling or new power plants. We need to get efficient), Time, January 12, 2009. 8. Bezpieczeństwo elektroenergetyczne w społeczeństwie postprzemysłowym na przykładzie Polski. Monografia opracowana pod redakcją J. Popczyka, Wydawnictwo Politechniki Śląskiej, Gliwice, 2009. 9. Bartodziej G., Tomaszewski M., Polityka energetyczna i bezpieczeństwo energetyczne. Wydawnictwo Nowa Energia, Racibórz, 2009. 10. Problemy rozległych awarii sieci elektroenergetycznych, pod redakcją G. Bartodzieja i M. Tomaszewskiego, w druku (Wydawnictwo Nowa Energia). 11. Grunwald M., Going Nuclear (Proponents tout atomic energy as a clean, carbon-free alternative to coal and oil. But could sink nukes again), Time, January 12, 2009.

Stanisław Czapp / Gdansk University of Technology

Author / Biographie

Stanisław Czapp Gdańsk / Poland Assistant Professor at the Department of Electrical Power Engineering of the Faculty of Electrical and Control Engineering at the Gdansk University of Technology. He graduated from the Faculty in 1996 and received a Ph.D. degree in technical sciences in 2002. His scientific activities are connected with electrical equipment and installations, especially in the area of protection against electric shock.

Current distortion in lighting systems and its impact on power supply installations

CURRENT DISTORTION IN LIGHTING SYSTEMS AND ITS IMPACT ON POWER SUPPLY INSTALLATIONS Stanisław Czapp PhD. Eng. / Gdansk University of Technology

1. CONSTRUCTION OF DISCHARGE LAMPS AND ITS IMPACT ON LOAD CURRENT 1.1. Light sources and ballast-ignition circuits The following are among the most popular discharge light sources: • low-pressure mercury lamps (tubular fluorescents and compact fluorescents), • high-pressure mercury lamps, • metal halide lamps, • high-pressure sodium lamps, • low-pressure sodium lamps, • induction lamps. It is characteristic of discharge lamps that in addition to a light source they also require a stabilising ballast-ignition circuit in order to function properly. This circuit starts the lamp and stabilizes the level of discharge between its electrodes. Depending on lamp type, starting requires voltage ranging from hundreds of volts to a few kilovolts while in those circuits which allow for a hot restart of a high-pressure lamp after a voltage dip (e.g. stadium lighting) the value reaches several dozen kilovolts. Discharging in lamps has a falling current-voltage characteristic. In order to avoid damage to the lamp, current limiting ballast should be used which sets the working point of the circuit. In conventional solutions this function is filled by an inductor or a capacitor. Majority of lamps are equipped with non-linear inductors which causes the power factor of the circuit to drop to the level of 0.5. The power factor may be improved by installing a capacitor for individual compensation. Discharge in the arc tube may be reflected by non-linear impedance. Taking into account the non-linearity of inductor and the presence of capacitor, the current load on the lamp is distorted. The distortion may also be significant in lamp with electronic ballast. Figure 1 presents examples of discharge lamp circuit diagrams. In the diagrams from 1a to 1d the arc tube is powered by 50 Hz voltage and fittings includes inductor, ignition module and a compensating capacitor. Figure 1e presents power supply block diagram of a tubular fluorescent with electronic ballast. In this case, the arc tube receives high frequency voltage - approximately 25÷50 kHz. The circuit of electronic ballast lamp is more advanced [19], but with the use of high frequency current the luminous efficacy of the lamp [23, 25, 31] increases and smooth dimming control is made possible. Lamp construction and used fittings affect the waveform of input current [6, 8, 9, 13, 39, 33] Lamps of similar characteristics such as luminous flux, colour temperature or colour rendering index may differ significantly in the waveform of load current.

Abstract The most of commonly used energy saving lighting systems have a distorted load current. In some cases distortion of the load current is significant and has an essential impact on overcurrent devices, cables and supplying transformer selection. The paper presents a spectral analysis of the discharge lamps load current and the principles of overcurrent devices and cables selection in lighting installations. Attention is also given to the problem of supplying transformer derating for nonsinusoidal load currents.

Stanisław Czapp / Gdansk University of Technology

26  





 



 













    







 











 

  Fig. 1.  Examples of circuit diagrams of discharge lamps: a) single tubular fluorescent lamp with conventional ballast; b) double tubular fluorescent lamp set in anti-stroboscopic arrangement; c) high-pressure mercury lamp; d) high-pressure sodium lamp; e) block po  wer supply diagram for a tubular fluorescent lamp with electronic ballast [10]; C – capacitor for improving power factor, L – inductor,  UZ – ignition module Z – ignitor,   1.2. Spectral analysis of load current of discharge lamps The following lamps were selected for the analysis:  a) compact fluorescent lamp with electromagnetic ballast,   b) compact fluorescent lamp with electronic  ballast,   c) high-pressure mercury lamp,   d) induction lamp,   e) high-pressure sodium lamp,   f) low-pressure sodium lamp,   g) tubular fluorescent lamp with electromagnetic ballast,   ballast and dimmer,  h) tubular fluorescent lamp with electronic   i) metal halide lamp.  Current spectral analysis of the lamps listed in items a) to f) was carried out for steady state with hot   lamps under rated voltage. The results are presented in this part of the paper. The analyses of the lamps men-

     tioned in items g) to i) are presented separately since they were conducted in varying operating conditions, i.e.,   for the tubular fluorescent with inductor the effect of the degree of compensating the reactive power on the waveform of load current (point 1.3), for the tubular fluorescent with electronic ballast the effect of factory fitted dimmer was investigated (point 1. 4), while for the metal halide lamp (point 2.1) the analysis was extended to a three-phase system which allowed for investigating the current in the neutral conductor.

Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig.2. Load current analysis of a single fluorescent compact lamp with electromagnetic ballast (due to the transfer ratio of the measuring transducer, current and power values should be divided by 10)

Figure 2 presents current load analysis of a single compact fluorescent lamp equipped with a classic ballast-starter circuit. The lamp uses inductor as ballast but is not equipped with a capacitor. This affects the power factor which amounts to approximately 0.53. Thanks to such an arrangement the load current is of relatively small distortion. Aside from the fundamental component the current flow is dominated by the 3rd harmonic and the total harmonic distortion is THDi = 14%.

Current distortion in lighting systems and its impact on power supply installations

Higher degree of distortion of the load current characterises the compact fluorescent lamp with electronic ballast. From the point of view of lighting benefits and durability this lamp presents a better solution than a fluorescent lamp equipped with conventional stabilization circuit. It is also characterised by a higher power factor. Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 3. Load current analysis of a single fluorescent compact lamp with electronic ballast (due to the transfer ratio of the measuring transducer, current and power values should be divided by 10)

However, considering its impact on electrical installation it may cause greater problems. The total harmonic distortion of current is very high and reaches over 96%. There is also a significant participation of odd harmonics from 3rd to 15th. The crest factor is very high, reaching the value of 2.84 - this information is of crucial importance in selecting protective devices. Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 4. Load current analysis of high-pressure mercury lamp equipped with inductor and capacitor

High pressure mercury lamp equipped with inductor and capacitor (Fig. 4) has load current which is quite substantially distorted. The total harmonic distortion is THDi = 34%, and the dominating harmonics are 3rd, 7th and 11th. The crest factor is smaller than in the case of the compact fluorescent with electronic ballast and has the value of 2. Figure 5 presents the load current of induction lamp. Induction lamps may be classified among mercury lamps but remain particular sources of light having extremely high durability of 60 000 hours. This source of light is powered by current of frequency in the megahertz range but the current from the power network is not strongly distorted. The current total harmonic distortion amounts to THDi = 12%. The power factor is maintained at a very high level reaching the value of 0.98. Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig.5. Load current analysis of induction lamp (due to the transfer ratio of the measuring transducer, current and power values should be divided by 10)

Stanisław Czapp / Gdansk University of Technology

In the high-pressure sodium lamp (Fig. 6) the current waveform is similar to the one in high-pressure mercury lamp. The total harmonic distortion of current is also similar amounting to THDi = 36%. However, the profile of individual higher harmonics is somewhat different with 3rd, 7th and 9th being the dominating ones. Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 6. Load current analysis of high-pressure sodium lamp

Low pressure-sodium lamp is characterised by a low degree of distortion in load current (Fig. 7). The total harmonic distortion amounts to THDi = 8%, and the crest factor only slightly exceeds the value of a 1.41 similarly to undistorted load. Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 7. Load current analysis of low-pressure sodium lamp (due to the transfer ratio of the measuring transducer, current and power values should be divided by 10)

1.3. Impact of reactive power compensation on current waveform Current distortion in lamps with conventional ballast is connected mainly with the absence or presence of a capacitor for individual reactive power compensation in the luminaire. Fluorescents without capacitors (Fig. 8), are characterised by a low power factor of approximately 0.5 but they load current is of low distortion (THDi = 9%). Use of a capacitor results in increasing the distortion of load current. If a capacitor recommended by the producer is used (Fig. 10) then the total harmonic distortion quadruples (THDi = 39%), whereas with the use of a capacitor of lower capacitance then recommended by the manufacturer (Fig.9) the power factor reaches only the value of 0.68 but the current distortion is not as strong (THDi = 16%).

Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 8. Load curent analysis of tubular fluorescents (twin tube luminaire) with inductor and no capacitor (due to the transfer ratio of the measuring transducer, current and power values should be divided by 2)

Current distortion in lighting systems and its impact on power supply installations

Odd harmonics

Current waveform in 40 m s

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 9. Load current analysis of tubular fluorescents (twin tube luminaire) with inductor and capacitor of lower capacitance than recommended by manufacturer (due to the transfer ratio of the measuring transducer, current and power values should be divided by 2) Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 10. Load current analysis of tubular fluorescents (twin tube luminaire) with inductor and capacitor of capacitance recommended by manufacturer (due to the transfer ratio of the measuring transducer, current and power values should be divided by 2)

Use of capacitor in the luminaire is meant to limit reactive component of current from the network. However, it should be emphasized that only the fundamental harmonic may be limited. This may be noticed in analysing the effective value of individual harmonics in Figures 8, 9 and 10. With the use of a capacitor the effective value of the fundamental harmonic decreases while the effective value of individual harmonics remains the same or increases slightly. Since the current total harmonic distortion is defined as:

I THDi = ∑  h h=2  I1 h=n

  

(1)

Where: Ih – effective value of the h order harmonic, I1 – effective value of the fundamental, it is quite natural that it will increase with the decreasing fundamental even if the effective value of higher order              harmonics remains unchanged.            Based on the analyses contained in the publications of Z. Gabryjelski and Z. Kowalski [10] it may be con             cluded that the participation of individual harmonics Ah, drawn from the network by a complete luminaire is    participation   in  directly     that many times greater from their the current flowing through the light source AhL,as             the natural power many times the power factor for the fundamental λ1 will be greater after compensation from  factor λn (no capacitor). Assuming that the natural power factor is 0.5 and after the use of capacitor 0.95, the  participation of the third harmonic in lamp’s current at the level of 0.1 (10%) without compensation, will result  after compensation in the increase of that harmonic in the current drawn from the network to the level of:    (2)             



 representing a nearly double increase.  Based  on the above analysis it may be concluded that in a facility  equipped with a large number of dis         charge lamps, in order  to  decrease the total harmonic distortion of load current synonymous with    which  is  lowering voltage distortion at the supply station it may be beneficial to use capacitors of lower capacitance than            manufacturer recommends or to remove them from luminaires.    

Stanisław Czapp / Gdansk University of Technology

1.4. The effect of lamp dimmer Discharge lamps require sophisticated and expensive electronic ballast circuits for smooth dimmer control over the luminous flux intensity. Block diagram of such a circuit is presented in Figure 1e. The lamp receives high frequency current thanks to which the current may be controlled without negative effects which would have appeared at the frequency of 50 Hz. It turns out that smooth control over the luminous flux of fluorescent lamps does not have to mean high current distortion as is the case with incandescent lamps. As it stems from the waveforms presented in Figures 11, 12 and 13, decreasingly smaller luminous flux is obtained at the cost of having a certain degree of current distortion but even with maximum dimming of the investigated luminaire (a few percent of luminous flux) the level of distortion is not very high. Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 11. Load current analysis of a tubular fluorescent with electronic ballast allowing for control over luminous flux. The dimmer was set at the maximum level of luminous flux (due to the transfer ratio of the measuring transducer, current and power values should be divided by 10).

Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 12. Load curent analysis of tubular fluorescent with electronic ballast allowing for control over luminous flux. The dimmer was set at the medium level of luminous flux (due to the transfer ratio of the measuring transducer, current and power values should be divided by 10)

Odd harmonics

Current waveform in 40 ms

Even harmonics

Characteristic values

Spectral characteristics of current

Fig. 13. Load current analysis of a tubular fluorescent with electronic ballast allowing for control over luminous flux. The dimmer was set at the minimum level of luminous flux (due to the transfer ratio of the measuring transducer, current and power values should be divided by 10).

It should be pointed out that decreasing of luminous flux is accompanied by a decrease in effective value of fundamental harmonic while the effective values of individual higher order harmonics remain practically unchanged. Dominant higher harmonic is 3rd one. Along with decreasing the luminous flux, there is a noticeable drop in the power factor from the value of 0.97 at full luminous flux to 0.80 at the minimum luminous flux level.

Current distortion in lighting systems and its impact on power supply installations

2. IMPACT OF NON-LINEAR LOAD ON SELECTION OF PROTECTIVE DEVICES AND CONDUCTORS 2.1. Load current and selection of conductors in installations with non-linear loads In lighting installations, due to the presence of current harmonics, overload of phase conductor and neutral conductor are to be expected. Currents with harmonics cause temperature rising of phase conductor, while due to significant load on the neutral conductor the current-carrying capacity of the entire system may be reduced. Particular attention should be paid to the neutral conductor [7, 11, 32]. In a single-phase circuit, the neutral current is identical to the current in the phase conductor. However, certain problem may appear in a three-phase circuit since in some situations the current in the neutral conductor may be of higher value than the currents in phase conductor even with symmetric phase current. In a three-phase symmetrical circuit the waves of the first harmonic are shifted in relation to each other 2ð   2p

by the angle of 120° h 33  . Higher harmonics of the h order are shifted by h 3 . Triplen harmonics, e.g., 3rd, h 9th, 15th, 27th etc. make the expression 3 an integer so they will be in phase with each other. Based on the above it may be concluded that the current triplen harmonics, flowing in separate phases will sum up arithmetically in the neutral conductor. Table 1 presents expected values of current in the neutral conductor depending on the load of separate phases and the participation of the 1st, 3rd and 9th harmonics. Table 1. Effective value of current in phase and neutral conductors with varied phase load for distorted waves with participation of 1st, 3rd and 9th harmonics. IL1 [A]

IL2 [A]

IRMS

100 100 100 100 100

15 33 45 55 33

0 0 0 0 15

101 105 110 114 105

100 100 100 100 100

15 33 45 55 33

0 10

0 3

0 0

0 10, 4

100 100

33 33

9. IRMS symmetrical load 0 101 0 105 0 110 0 114 15 105 asymmetrical load 15 106 0 105

IL3 [A] 9.

IRMS

IN [A] IRMS

100 100 100 100 100

15 33 45 55 33

0 0 0 0 15

101 105 110 114 105

45 99 135 165 109

100 100

33 33

15 0

106 105

124 113

It is not hard to notice that with a substantial content of the 3rd harmonic, the current in neutral conductor may be of greater value than the current in the phase under the highest load (shaded area in Table 1). Selection of conductor cross-section based on the maximum load of phase conductors may lead to overloading and damaging the neutral conductor. The phenomenon of summation of triplen harmonics in the neutral conductor in practice occurs partly and is dependant on load asymmetry. The actual current in the neutral conductor contains various harmonics, also no triplen harmonics. Figures 15 and 16 present currents in a model laboratory installation while the ones in Fig. 17 and 18 represent actual working installation in a large facility equipped with numerous metal halide lamps. Lab tests were performed on three identical 400 W metal halide lamps connected in a symmetrical 3-phase circuit. The conducted analysis covered current waves in the phase conductor of each lamp, as well as in the neutral conductor.

Current waveform in 40 ms

Spectral characteristics of current

Rys. 14. Load current of a metal halide lamp

Stanisław Czapp / Gdansk University of Technology

The waveforms presented in Fig. 14 show that the load is significantly distorted and is characterised by a crest factor equal to 2.79. As a result of numerous measurements, it may be concluded that the THDi reaches the values in the range of 39÷54%; with the parameter changing at random, similarly to the effective value of the input current.

Current waveform in 40 ms

Spectral characteristics of current

Fig. 15. Analysis of load current in neutral conductor of a 3-phase circuit symmetrically loaded with three metal halide lamps (1 lamp/phase)

Current flowing in the neutral conductor of a 3-phase circuit symmetrically loaded with three 400 W metal halide lamps (Fig. 15) is dominated by triplen harmonics, especially the 3rd harmonic. The THDi is in the range of 300%. Despite symmetrical load the current in the neutral conductor reaches nearly 70% of the current value in phase lines. Distortion of current drawn by a group of several dozen 400 W lamps (Fig.16) is much greater than under laboratory conditions. The THDi in phase conductors of the installation of the investigated facility reaches the level of 70÷220%, in comparison with the value of 39÷54% measured in the laboratory. Attention is drawn to the nearly three times greater effective value of current– 92. 4 A, in relation to the current of the fundamental harmonic (38.36 A).

Current waveform in 40 ms

Spectral characteristics of current

Fig. 16. Analysis of load current of a group of metal halide lamps

The same lamp or group of lamps will draw current of different waveform depending on the type and power of the source (transformer, thyristor frequency converter) [13]. Single lamp should fulfil the requirements of the standard PN-EN 61000-3-2:2007 [27] regarding acceptable level of current distortion. However, its load is usually of lower distortion than in a group of lamps powered form the same source. Lamp group constitutes a load of power from a few to several dozen kilowatts. This may lead to a situation where a single lamp fulfil the standard requirements regarding current distortion[27], but a group of lamps does not [16].

Current waveform in 40 ms

Spectral characteristics of current

Fig. 17. Analysis of load current in neutral conductor of a lighting circuit containing a large number of metal halide lamps.

Current distortion in lighting systems and its impact on power supply installations

Analysis of current in the neutral conductor of the circuit containing several dozen 400 W metal halide lamps shows (Fig. 17) that the 3rd harmonic is the dominating one. Based on the analysis it may be concluded that current in the neutral conductor has higher value than current in phase conductors even with certain small asymmetry of load. The effective value of this current is over 170 A, while the effective value of the current in phase conductors is approximately 90 A, which is of significance in selecting the cross-section of neutral conductor. The neutral conductor cross-section in installations of non-linear loads should not be any smaller than the cross-section of phase conductors

2.2. Selection of overcurrent protective devices Protection against overloads and short-circuits is provided by circuit breakers and fuses. In selecting rated current of protective device one should be guided by the effective value of current with providing for currents of higher harmonics. Taking into account higher harmonic currents the effective value of current in phase conductors of a single lamp may be a dozen or so percent higher than in the case of the fundamental harmonic (Fig. 14). The participation of higher harmonics in current may be higher since the combined power of the lamp constitutes significant transformer load. Discharge lamps are characterised by increased current at the moment of switching on. The transient  current value is about 1, 4÷2,01 times greater than rated current value. Data on transient current is provided by lamp manufacturer. Fig. 19 presents changes in current drawn by high-pressure mercury lamp and high    pressure sodium lamp from the point of switching on to reaching steady state [10, 23]. The transient current    gradually decreases within a period of few minutes to the rated current value. Due to the increased current value right after switching the lamp on, the rated current of the circuit  breaker should be greater than it might stem from the maximum load in steady state. In a circuit with  current    discharge lamps with cacapitor, it may be concluded for the sake of simplification that the continuous rated  current of the circuit breaker Inw should be high enough not to allow its overload release to react in a given  time period to the load current expressed as a multiple of lamp’s rated current Ilam (Tab. 2) [15]. As it stems  from Table 2, the rated current of the circuit breaker should be at least 25% greater than the load on the lamp  in steady state.  Tabl. 2. Estimated values of transient current and its flow time in circuits of discharge lamps with capacitors  Time  4 min 2 min ∞ Load current





1,25×Ilam





1,6×Ilam



1,8×Ilam

 

The changes presented in Fig. 18 apply to the effective value, and as it stems from the oscilograms pre in the previous point, the load current may be strongly distorted. Study results presented in the publicasented tion  of M. Walejewski [34] show that the current right after switching the lamp on may be of higher distortion  than in its steady state. In protective devices selection it is also important whether the current waveform is characterised by high crest factor. Electromagnetic release of the circuit breaker reacts to the peak load value  and in order to avoid nuisance tripping the peak current value of non-tripping current of the circuit breaker  be greater than the instantaneous value of the current i present in all foreseen transient state [22]. should max  

    



  

 



















            Fig. 18. Changes of current load for high-pressure mercury and sodium lamps from ignition to steady state[10, 23];  In – current load in steady state

1 Peak value of current at switching on of a lamp equipped with parallel capacitor may amount to several dozen amperes but the pulse will be of very short duration (hundreds of microseconds). Such phenomena is not considered in this paper.

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                              University   Czapp   Stanisław /Gdansk of Technology            

     Taking into account the circuit breaker characteristic t-I and the description presented in Fig. 19 this can    be expressed through the following relationship:   0,8⋅  2⋅ Ii ≥ k b ⋅ imax           (3)     where:   kb – protection factor kb ≥ 1,25.       breaker’s  short-circuit In connection with the above, the effective value of current setting Ii of the circuit                        release should fill the condition:     25 ,  1 1,1        Ii ≥ ⋅i ⋅i (4)  max  max   ≈   0,8⋅ 2    Current setting of the short-circuit release in distorted flow should be greater from the current setting of    a sine wave in relation to:       k s     I       = ⋅ I i_sin    (5)  i_odkszt 2  Where:   Ii_odkszt – current setting of a short-circuit release at distorted flow            Ii_sin  – current setting of a short-circuit release at sine wave            ks – crest factor         t                  -20% +20%        Fig. 19. Time-current characteristic of the circuit breaker: release,  Ir – current setting of overload        current of short-circuit release Inz – non-tripping   Ii – current setting of short-circuit release   I Ir Inz Ii  fluorescent lamps     If the circuit contains compact characterised by the load current in Fig. 3, then the   k / 2 = 2.84 / 2 = 2 from        the current setting of short-circuit release should be greater by the ratio of s            current setting for undistorted This should be the procedure circuit breakers of adjustable current flow.  with       setting of short-circuit release. In typical circuit breakers of B, C or D characteristic, there is no possibility of setting short-circuit  are presented inFig. 20. Charrelease. Non-tripping  currents of short-circuit releases of circuit breakers    Inz    acteristic type of B, C  or D should be  selected depending on transient current and crest factor. In each of the          cases, the peak value of release’s non-tripping current inz should be greater than the instantaneous current value imax appearing in all foreseen transient phases.  In the case of circuits protection by fuses, in order to avoid the melting of fuse element at ≥ (1, 4÷1,8) × Ilam , with greater lamp start-up, the rated current of the fuse should be equal to Inb       values   applying to simultaneous switching on of lamps of extended start-up time. [15]. Fuse of the gG or gF type  are employed in lighting circuits and there is no need for making additional correction of the rated current  of the fuse due to crest factor. Correction may be necessary only in the case of fuse with narrow fuse   elements (aR or gR fuse for semiconductor devices) [21].                                      



  





 





 

 

 

 

 



 







  Current distortion in lighting systems and its impact  on power supply installations                                                  









                             Fig. 20. Non-tripping currents (effective value) of short-circuit releases       of    circuit breakers     2.3. Selection of conductor                   The guidelines for dimensions of conductors in circuits loaded withcurrents containing harmonics may be             found in the standard PN-IEC 60364-5-523:2001 [28] “Current-carrying capacities in wiring systems” , Appendix              C “Impact of higher order harmonic currents on three-phase circuits of symmetrical load”. If participation of exceeds     in     3rd harmonic 15% thanthe correction coefficients presented Table 3 should be used. In order  the  the required current-carrying capacity of a conductor in distorted load, the value of current load of  to obtain the phase or neutral conductor core should be divided by a given coefficient form Table  3. The correction coef          ficients apply only to those lines in which the neutral conductor is one of four or five conductors of multi-core  conductor cable and is of the same cross-section and material as phase conductors. The coefficients values were   calculated based on the participation of the 3rd harmonic. If the participation of other triplen harmonics ex  ceeds the level of 10% of the fundamental harmonic, then their part in the load of the neutral conductor should            also be taken into account.   Table 3. Correction coefficients for currents of higher harmonics in 4-conductor and 5-conductor multi-core conductor cables [28]         Correction coefficient   in phase  Participation of the third harmonic    Selection of conductor cross-section based on Selection of conductor cross-section based on  conductor current  [%]   the current value in phase conductors the current value in neutral conductor     0–15 1,0 –     15–33 0,86 –     33–45 – 0,86     > 45 – 1,0       If the number of loaded conductor cores is greater than four, then based on [3] the conductor current   following   carrying capacity may be calculated in the way:           







  



  

 







(6) 

where: capacity of a conductor of N loaded IzN – current-carrying   cores Iz1 – current-carrying capacity of a single-core conductor Nz – number of conductor cores under load The above relationship applies to those conductors in which all the conductor cores are under the same load. Lack of load or insufficient load of one or more cores has a positive effect on the current-carrying capacity of the entire conductor.

Stanisław Czapp / Gdansk University of Technology

          

n-krotne z mniejs z enie obciąż alnoś ci prz ewodu wieloż yłowego

      

2,00 1,95 1,90 1,85 1,80 1,75 1,70 1,65 1,60 1,55 1,50

 

5 1





L icz ba obciąż onych ż ył 



Fig. 21. Dependence between current-carrying capacity of a multi-core cable and the number of conductor-cores.

Fig. 21 illustrates decrease in current-carrying capacity of a multi-core conductor cable depending on the  number of conductor-cores under load in accordance with the relationship (6). With a five-core cable of equal  load on conductor-cores there occurs a 1.7 times decrease of the current-carrying capacity of each conductorcore in comparison with single conductor-core under load, whereas with seven conductor-cores under load, the current-carrying capacity decreases almost twice. Guidelines contained in the Appendix C of the standard [28] are not very exact. More precise guidelines regarding selection of conductor cross-section in circuits of distorted current are given in the works [12, 24] and are presented in Table 4. The correction factor r included in Table 4 by which the current-carrying capacity of three conductor-cores under load should be multiplied by [28], was made dependant on the relation of the current in neutral conductor to the current in phase conductor, as well as to the placement of conductors. In certain cases, it is recommended to use neutral conductor N of a larger cross-section than the cross-section of phase conductors or to use two neutral conductors. Table 4. Correction factors of load of permanently placed 4-core conductors of phase circuits depending on the relative value of current in neutral conductor N (PEN) [12,24] Relation of current in neutral conductor to current in phase conductor v=

IN IL

v ≤ 0,2 0,2 < v ≤ 0,4 0,4 < v ≤ 0,6 0,6 < v ≤ 0,8 0,8 < v ≤ 1,0 1,0 < v ≤ 1,2 1,2 < v ≤ 1,4 1,4 < v ≤ 1,6 1,6 < v ≤ 1,8 1,8 < v ≤ 2,0

A2 B1 in tube or strip

in thermo-insulated wall single-core 1,00 0,97 0,94 0,91 0,87 0,83 (0,78) (0,72) (0,65) (0,57)

multi-core 1,00 0,97 0,94 0,91 0,87 0,83 0,78 0,72 0,65 0,57

Wiring system C

on surface, on wall, contact between conductors single-core 1,00 0,97 0,94 0,91 0,87 0,83 (0,78) (0,72) (0,65) (0,57)

multi-core

Correction factor r 1,00 0,97 0,94 0,91 0,87 0,83 0,78 0,72 0,65 0,57

F no tube or strip away from wall 1,0 × d 0,3 × d single-core no contact multi-core single layer bundle 1,00 0,97 0,95 0,93 0,89 0,85 (0,80) (0,73) (0,66) –

1,00 0,96 0,93 0,90 0,86 0,82 (0,77) (0,71) (0,64) –

Remarks: 1. Current-carrying capacity Iz3 from PN-IEC60364-5-523 (for current loaded 3-core conductors) should be multiplied by the correction factor r, in order to obtain the current-carrying capacity of 4-core conductors of identical cores (or 4 identical single-core conductors) Iz4 = r × Iz3, where the neutral core (neutral conductor) is loaded to the degree of v. All current values are effective values. 2. In TN-C system the relation v means the relative value of current in PEN conductor. TN-C is not recommended at higher values of v, for example v > 0.5. 3. Values of the correction factor r given in brackets, mean that in those cases, one should consider using the neutral conductor N of greater cross-section than the cross-section of phase conductors or use two neutral conductors

Current distortion in lighting systems and its impact on power supply installations

Information about the effective value of load current taking into account higher harmonics and the current value in the neutral conductor is not sufficient to define the lowest acceptable cross-section of conductor. Harmonics of high orders (e.g. 23rd, 49th.) cause greater re-dimensioning of conductor than if the current contains mostly harmonics or relatively low orders (e.g. 5th, 7th), even if in both cases the THDi factor is identical. The higher the harmonic order the greater the increase in conductor’s resistance in relation to the condition when the conductor carries undistorted load (as a result of the skin effect phenomenon). Additional power losses occur in the conductor which means a rise in its temperature. Harmonics of higher orders will have a greater degree of impact on large cross-section conductors than on small cross-section ones. Precise consideration of the impact of higher harmonics on current rating of conductors is possible [1, 14], but it is a complex task. The work of Ch. Demoulias and partners [1] contains analysis of the impact of currents of various waveforms on the current-carrying capacity of 16, 120 and 240 mm2 cross-section 4-core conductors . The analysis was conducted for a scenario where all the cores of the conductor are of identical cross-section or when the neutral conductor core is of smaller cross-section. The conclusion of the analysis is that with currents of significant triplen harmonics (impulse power supplies of electronic equipment, compact fluorescents) the current-carrying capacity of conductors becomes substantially reduced (by 29÷46%). In load current of low participation of triplen harmonics, the current-carrying capacity should be reduced by several percent.              3. REDUCTION OF ACCEPTABLE LOAD ON TRANSFORMER SUPPLY OF LIGHTING INSTALLATIONS             into      Transformer losses may  be divided “no-load” and “load”. The no-load losses are not dependant on               load and therefore also not on whether the load current is distorted or not. The load losses may  be divided into                ones  primary and secondary ones. Primary losses take place in the windings, while  the secondary are a result                   of eddy currents in the windings coming from leakage fluxes and power losses taking place in metalparts (e.g.                    tank). Current of higher harmonic orders flowing through transformer winding cause increase in secondary       which  with  distorted  load current   losses. Rise in load losses means increase in the temperature of windings of             effective value close to transformer’s rated current may mean exceeding the acceptable temperature level for             transformer operation. There are several methods [2, 4, 5, 17, 18, 26, 29, 35] for transformer’s derating which              allows for ensuring that at a given distorted current waveform, the transformer will not be thermally overload           ed.  Unfortunately, the value of transformer’s reduced power varies depending on the method of determining it          and the differences may be substantial. The method presented below is the one defined in the standard PN-EN  [29].         50464-3:2007  Transformer at distorted current waveform may be loaded with the power of: 



     S  S H = n   K

 (7)   where:   SH – apparent power load which can be placed on the transformer at a given distorted waveform,    transformer Sn – apparent power rating,    K –factor for transformer derating.   K is determined based on the following relation:   2 2  e  I1  h=n Ih    q          ⋅ h  K = 1 +    ⋅    ⋅∑ (8)  + e IÓ h=2 I1     1                                where:    e – the eddy current loss due to sinusoidal current of fundamental frequency divided by the loss to a d.c. current to  equal the  r.m.s. value of the sinusoidal current, both at reference temperature,             I1 –effective value of the fundamental harmonics,    IΣ – effective of load current harmonic, value   with          Ih – the hth  harmonic current,     h – harmonic order, q – exponential constant, dependent on winding type and current frequency (1,5 for transformer of low voltage     windings of foil; 1,7 for transformers with round or rectangular wire in both the low and high voltage    made     windings).                                                             

                  Stanisław Czapp / Gdansk University of Technology                          If a 630 kVA rated power transformer loaded with current of the waveform presented in Fig.15 (pow-     was      ering a single lamp under lab conditions), then following power could be drawn from it for long duration:             (9) 



                 so its use would be limited to the level of 81% (assuming e = 0.05 and q = 1.7). In a facility with a large  number of lamps which constitute the dominant transformer load, current distortions are greater than under conditions        current    laboratory (Fig. 17) and are difficult to predetermine [20].With such waveform, the power  which can be provided by the transformer is even smaller and equals 440 kVA (0.7×Sn).  4. CONCLUSIONS   Distortion of load current in lighting systems depends on the type of installed light source and the ballastignition circuit, as well as the power source rating. The impact of current distortion should be taken into consideration in selecting protective devices, conductors and power transformer. Therefore, it is advisable to examine quite closely the properties of lighting devices, which are to be included in the installation, especially in the area regarding the participation of harmonics in the load current. This is particularly important when the devices are to constitute a substantial participation in facility’s combined power demand and transformer’s load.

LITERATURE 1. Demoulias Ch., Labridis D.P., Dokopoulos S.P., Gouramanis K., Ampacity of Low-Voltage Power Cables Under Nonsinusoudal Currents. IEEE Transactions on Power Delivery, 2007, vol. 22, no. 1, s. 584–594. 2. Desmet J., Lemcko L., Harmoniczne. Dopuszczalna obciążalność i dobór transformatorów do pracy z prądem odkształconym. Leonardo Power Quality Initiative. Jakość zasilania – poradnik, cz. 3.5.2, listopad 2005. 3. Det Norske Veritas. Rules for classification of ships. Part 4 – Machinery and Systems – Main Class. Chapter 4 – Electrical Installations. Edition 1999. 4. Faiz J., Sharifian M.B.B., Fakheri S.A., Sabet-Marzooghi E., Derating of Distribution Transformers for Non-sinusoidal Load Currents Using Finite Element Method. Iranian Journal of Science & Technology, Transaction B, 2004, vol. 28, no. B3, s. 315–322. 5. Filtracja i detekcja harmonicznych. Schneider Electric. Materiały firmowe. 6. Gabryjelski Z., Świetlówki kompaktowe jako źródło zaburzeń elektromagnetycznych. Przegląd Elektrotechniczny, 2007, nr 9, s. 100–103. 7. Gabryjelski Z., Praca świetlówek kompaktowych w sieci trójfazowej. Przegląd Elektrotechniczny, 2007, nr 9, s. 42–43. 8. Gabryjelski Z., Odkształcenie prądu w obwodach lamp fluorescencyjnych i wyładowczych połączonych ze statecznikiem indukcyjnym. Archiwum Elektrotechniki, 1982, t. XXXI, z. 1–2, s. 125–136. 9. Gabryjelski Z., Odkształcenie prądu w obwodach lamp fluorescencyjnych i wyładowczych połączonych ze statecznikiem pojemnościowo-indukcyjnym. Archiwum Elektrotechniki, 1982, t. XXXI, z. 3-4, s. 571–581. 10. Gabryjelski Z., Kowalski Z.: Sieci i urządzenia oświetleniowe. Zagadnienia wybrane. Politechnika Łódzka. Łódź 1997. 11. Gabryjelski Z., Kowalski Z.: Przyczyny obciążania przewodów zerowych w sieciach oświetleniowych. Gospodarka Paliwami i Energią, 1977, nr 7, s. 21–23. 12. Hering E., Leitungen mit vier belasteten Leitern. Elektropraktiker, 2004, nr 9, s. 722–726. 13. Herlender K., Cadler E.: Wpływ sposobu zasilania nowoczesnych układów oświetleniowych na jakość energii elektrycznej. Wiadomości Elektrotechniczne, 2006, nr 3, s. 30–32. 14. Hiranandani A.: Calculation of Cable Ampacities Including the Effect of Harmonics. IEEE Industry Applications Magazine, March/April 1998, s. 42–51. 15. Instalacje elektryczne i teletechniczne. Poradnik montera i inżyniera elektryka. Verlag Dashöfer. Część 5. Zabezpieczenia w instalacjach elektrycznych. 16. Kasprzak A., Orlikowski M., Brodecki D., O pewnych aspektach EMC dotyczących powszechnego wprowadzenia świetlówek energooszczędnych. Przegląd Elektrotechniczny, 2007, nr 9, s. 104–105. 17. Kelley A.W., Edwards S.W., Rhode J.P. Baran M.E., Transformer Derating for Harmonic Currents: A Wide-Band Measurement Approach for Energized Transformers. IEEE Transactions on Industry Applications, 1999, vol. 35, no. 6, s. 1450– 1457. 18. Kuśmierek Z., Współczynnik obciążenia transformatora zasilającego odbiorniki nieliniowe i jego pomiar. Przegląd Elektrotechniczny, 2004, nr 6, s. 636–638. 19. Magdziak R. Układy zabezpieczeń w elektronicznych statecznikach świetlówek. Elektronizacja, 2000, nr 4, s. 18–19.

Current distortion in lighting systems and its impact on power supply installations

20. Musiał E., Czapp S., Opinia w sprawie zakłóceń wywołanych prądami wyższych harmonicznych w instalacji elektrycznej supermarketu OBI w Gdyni-Cisowej. Gdańsk 1999. 21. Musiał E., Bezpieczniki w nowoczesnych układach zabezpieczeń urządzeń niskiego napięcia. Ogólnopolskie Szkolenie Techniczne „Zabezpieczenia niskonapięciowych instalacji i urządzeń elektrycznych”. ENERGO-EKO-TECH, Poznań, październik 2001. 22. Musiał E., Zabezpieczanie silników zasilanych z pośrednich przemienników częstotliwości. INPE Informacje o Normach i Przepisach Elektrycznych, Miesięcznik SEP, 2004, nr 59–60, s. 3–35. 23. Musiał E., Przegląd elektrycznych źródeł światła. Główne właściwości i tendencje rozwojowe. INPE Informacje o Normach i Przepisach Elektrycznych, Miesięcznik SEP, 2006, nr 79, s. 3–66. 24. Musiał E., Obciążalność cieplna oraz zabezpieczenia nadprądowe przewodów i kabli. INPE Informacje o Normach i Przepisach Elektrycznych, Miesięcznik SEP, 2008, nr 107, s. 3–41. 25. Pabjańczyk W., Oszczędności energetyczne wynikające ze stosowania elektronicznych urządzeń stabilizacyjno-zapłonowych. Wiadomości Elektrotechniczne, 2000, nr 10, s. 540–543. 26. Pierce L.W., Transformer Design and Application Considerations for Nonsinusoidal Load Currents, IEEE Transactions on Industry Applications, 1996, vol. 32, no. 3, s. 633–645. 27 PN-EN 61000-3-2:2007 Kompatybilność elektromagnetyczna (EMC). Część 3-2: Poziomy dopuszczalne. Poziomy dopuszczalne emisji harmonicznych prądu (fazowy prąd zasilający odbiornika < lub = 16 A). 28. PN-IEC 60364-5-523:2001 Instalacje elektryczne w obiektach budowlanych. Dobór i montaż wyposażenia elektrycznego. Obciążalność prądowa długotrwała przewodów. 29. PN-EN 50464-3:2007 Trójfazowe olejowe transformatory rozdzielcze 50 Hz od 50 kVA do 2500 kVA o najwyższym napięciu urządzenia nie przekraczającym 36 kV. Część 3: Wyznaczanie mocy znamionowej transformatora obciążonego prądem niesinusoidalnym. (oryg.) 30. Różowicz A., Systemy świetlne jako źródło zakłóceń. Przegląd Elektrotechniczny, 2003, nr 4, s. 296–299. 31. Różowicz A., Skuteczność świetlna lamp fluorescencyjnych zasilanych prądem o różnej częstotliwości. Wiadomości Elektrotechniczne, 2004, nr 11, s. 15–18. 32. Rydzewski Z., Nowosielski J., Specyficzne cechy świetlówek jako odbiorników sieci trójfazowej niskiego napięcia. Przegląd Elektrotechniczny, 1973, nr 7, s. 331–335. 33. Starzak Ł., Bek S., Modelowanie kompaktowych lamp fluorescencyjnych do badań ich oddziaływania na sieć zasilającą. Przegląd Elektrotechniczny, 2007, nr 9, s. 106–107. 34. Walejewski M., Analiza jakości energii elektrycznej w instalacjach oświetleniowych. Praca dyplomowa magisterska. Politechnika Gdańska, Gdańsk 2006. 35. Yildirim D., Fuchs E.F., Measured Transformer Derating and Comparision with Harmonic Loss Factor (FHL) Approach. IEEE Transactions on Power Delivery, 2000, vol. 15, no. 1, s. 186–191.

Andrzej Graczyk / Wrocław University of Economics

Author / Biographie

Andrzej Graczyk Wrocław / Poland Head of the Environmental Economy Chair at the Wrocław University of Economics in Wrocław. Graduate of the National Economy Faculty of the Wrocław University of Economics, MA degree in 1978, Ph.D. - in 1988, habilitacja [second level doctorate] in 2005. In the years 1999–2005 Deputy Dean for Didactics at the Faculty of National Economy and starting 2005 Dean of the Faculty of Economic Sciences at the Wrocław University of Economics in Wrocław. Research areas related to environmental economics and environmental management, power management, theory and practice in sustainable development. In the years 2003–2004 he was the head of the team for financial and economic environmental development mechanisms of the Expert Council appointed by the Minister of the Environment. He is a member of the Scientific and Technical Council of Energa Group and Programme Council for Application of Advanced Technologies CATA.

Development of CO2 emission trading in the european union

DEVELOPMENT OF CO2 EMISSION TRADING IN THE EUROPEAN UNION1 Andrzej Graczyk / Wrocław University of Economics

THE CONCEPT OF EMISSION TRADING Tradable emission allowances/credits are a relatively new instrument for regulating pollution emissions (and emission reduction rate). The concept at its initial stage involved resignation from controlling the quality of the environment with norms and standards set for emitters. An agency (office) responsible for environmental control was to decide on the admissible or tolerable pollution load and the relevant number of emission allowances and next introduce them to the market, distributing them free of charge or selling the credits to emitters. The key element of the concept is the allowance/credit, which the emitters can sell and buy on the created secondary market. The demand for credits is created by allowance holders who may refrain from exercising the right to emit a specified quantity of pollutants, but to sell this right to another entity. Allowances may then be further sold and bought on the emission credits market. The motive underlying the transactions is the benefit enjoyed by the parties involved and the choice of the cheapest way of compliance with environmental regulations. Emitters whose costs of reducing emissions below the assigned limit are lower may lower their emission levels and sell extra emission rights to other emitters (with higher emission costs). For the latter the purchase of additional emission credits is more profitable than emission reduction. Trading will continue until the differences of marginal costs of emission reduction disappear. The credits market will reach equilibrium when the price is equal to marginal costs of all emission sources. Thus, emission trading will automatically satisfy the conditions for minimising social costs of reaching the specified environmental quality level. The projected emission reduction will be performed by those who can reach the target at the lowest cost. The emission credits market may – if it is properly designed – lead to a major drop of environmental protection costs of society in general, particularly as compared with an administrative regulating system, (emission standards). Tradable emission rights would be exercised wherever they are cheaper than the required measures reducing emissions. And on the contrary, they would not be applied should the drop of emission levels require smaller outlays than the purchase of relevant emission allowances. This means that any admissible pollution load for the environment could be attainable in this system at minimum overall social cost. The emission credits market may – if it is properly designed – lead to a major drop of environmental protection costs of society in general, particularly as compared with an administrative regulating system, (emission standards). Tradable emission rights would be exercised wherever they are cheaper than the required measures Abstract The article presents the concept of emission credits trading. The development of the market for emission trading in the European Union resulted from the lack of progress in ratifying the Kyoto Protocol, which was to open a global market. Several stages can be identified in the development of the European system for emission trading. The years 1997–2004 were devoted to preparing the political, conceptual and regulatory grounds for market development. The first stage, in the years 2005–2007, was a trial period, where emission allowances for voluntary participants were allocated at no cost by particular countries according to criteria set out on the basis of historical emissions. The second stage of implementing the emission trading system (2008–2012) overlaps with the first period of Kyoto protocol commitments where the allowance alloca-

tion method was uniform in all EU States. The participation of entities in identified sectors is mandatory. The distribution of tradable credits is free of charge but continuous to be based on historical emission data. A secondary emission credit market is developing. In the third period – in the years 2013–2020 – the range of market players will grow. Systematic development of the auction system for allowance distribution will follow. The development of the system for emission trading after 2020 will depend on the adoption of an international agreement on reducing emissions globally. The article is to present the development of the European Union market, which is the leader of applying market mechanisms to protect the climate.

Research project financed from the state budget for science in the years 2007–2009.

Andrzej Graczyk / Wrocław University of Economics

reducing emissions. And on the contrary, they would not be applied should the drop of emission levels require smaller outlays than the purchase of relevant emission allowances. This means that any admissible pollution load for the environment could be attainable in this system at minimum overall social cost.

FLEXIBLE MECHANISMS UNDER THE KYOTO PROTOCOL Introduction of new market solutions in limiting emission of greenhouse gases are connected with the Protocol to the United Nations Framework Convention on climatic changes adopted in Kyoto on 11 December 1997, further referred to as the Kyoto Protocol2. On 16 February 2005, the Kyoto Protocol came into force ratified by 55 countries in Annex 1, who in total emit at least 55% of the global CO2 emission as of 1990. The Kyoto Protocol introduced several mechanisms facilitating performance of commitments on emission reduction by exchange of the so-called reduction units between countries – Convention parties. The most important instruments for such cooperation are: • The Joint Implementation Mechanism – JI where the Emission Reduction Unit – ERU is obtained in joint implementation projects; • Clean Development Mechanism – CDM, where trade covers units of Certified Emission Reduction (CER); • Emission Trading Mechanism – ET, according to which Assigned Amount Units – AAU are traded. The primary aim of introducing market mechanisms, called flexible mechanisms, is the drive to reduce costs of implementing reduction objectives under the Kyoto Protocol. The mechanisms allow for the achievement of targeted emission reduction of these gasses on a global scale by trading CRU and ERU between parties to the Convention. At the same time, this new form of activating international cooperation has a considerable development potential. The solutions were adopted for a limited time period, up to the year 2012. Nevertheless, the European Union drives at concluding a new international agreement that will be binding after the year 2012. Therefore, we can expect that the mechanisms applied to that date will also function later. PREPARATORY MEASURES FOR CREATING A EUROPEAN MARKET FOR EMISSION CREDITS - 1997–2004 At the beginning of the nineties tradable allowances were deemed to be a controversial solution in many European countries. Emission trading was exercised on a limited scale, often as an experiment3. Proposals of introducing an international system for emission trading in greenhouse gasses appeared at the stage of preparing for the conference in Kyoto (1997). As there was no option for immediate introduction of the Protocol worldwide4, European Union States initiated action towards introducing emission trade within the Community. In 2000 work on emission trade gained impetus. The European Commission in March of that year published the “Green Paper on greenhouse gas emissions trading within the European Union”, and in November of the same year the European Parliament committed the Commission to prepare the emission trading scheme by the year 2005. In October 2001, Commission Communication from Goteborg for the European Council “A Sustainable Europe for a Better World: a European Union Strategy for Sustainable Development” confirmed the need to develop a European scheme for carbon dioxide emission trading. The Kyoto protocol was approved by the Council Decisions 2002/358/EC of 25 April 2002. The Community and its Member States agreed to jointly comply with the commitment to reduce anthropogenic greenhouse gasses according to the Kyoto Protocol. In the above period two EU countries implemented their own internal systems for emission trading – Denmark in 1999 (mandatory participations of the energy sector) and Great Britain in 2002 (voluntary participation for enterprises from all sectors). Additionally in third countries – Sweden, The Netherlands and Germany widespread research was carried out on the option of implementing tradable allowances, whereas France developed a scheme for voluntary agreements regarding reduction of greenhouse emissions which may evolve into emission trading. The sixth Community Programme5 specified reduction of greenhouse emissions as one of four priorities 2 Journal of Laws no 203, item 1684, of 17 October 2005. 3 These examples are given in the book by: Fiedor B., Graczyk A., Jakubczyk Z., Rynek pozwoleń na emisję zanieczyszczeń na przykładzie SO2 w energetyce polskiej, Wydawnictwo Ekonomia i Środowisko, Białystok 2002, pp. 39–42. 4 On 16 February 2005 the Kyoto Protocol came into force ratified by 55 countries, according to Annex I to the Protocol, that in total emitted at least 55% of CO2 in global terms in 1990. 5 Established by the European Parliament and European Council Decision No 1600/2002/EC (Official Journal L 242 dated 10.9.2002, p. 1).

Development of CO2 emission trading in the european union

in environmental sphere. The programme agrees that the Community is involved in reaching an 8 % reduction of greenhouse emission from 2008 to 2012 compared to 1990, and in the long term perspective global greenhouse emissions will have to be reduced by approximately 70% as compared to 1990. In connection with the above programme a European Parliament and European Council Directive was drafted on a system for trading GHG credits in the Community and to amend Directive 96/61/EC6. Directive 2003/87/EC7 was adopted in October 2003 with the aim of improving successful compliance with the commitment of the European Community and its Member States by effective European trade in GHG emission allowances with the least detrimental impact on economic development and employment8. It obliged EU Member States to establish national systems for GHG emission trading. The Directive stipulated that the system will be mandatory in all Community countries starting 2005. It projected limited trading in the Community as early as in 2005 in order to facilitate development of relevant strategies before open emission trade under the Kyoto Protocol in 2008.

THE FIRST STAGE OF MARKET DEVELOPMENT 2005–2007 The system for emission trading was introduced in two stages. The first stage (in the years 2005–2007) was a trial period, where emission limits for traders were allocated at no cost by particular countries according to criteria set out in the Directive on the basis of historical emissions (i.e. grandfathering method). Member States divided emission credits for 2298.5 million Mg of carbon dioxide with nearly 95% free of charge. The system covered emission of carbon dioxide generated by various heat and power plants with high emission levels and other power consuming industrial sectors, such as: incineration plants, oil refineries, coke plants, steel mills, cement factories, brick factories, glass mills, plants producing lime, ceramics, pulp and paper. The National Emissions Trading Schemes for the years 2005–2007 covered only one (CO2) of the greenhouse gasses and only part of the domestic emission. Due to the above, it was impossible to apply the Kyoto Protocol objectives as emission limits in the ETS. Nevertheless, Annex III to Directive 2003/87/EC required for the total number of allowances granted under ETS before 2008 to be in line with the drive to satisfy the Kyoto Protocol requirements. A significant change in the system also included a change in the procedures tor issuing emission allowances. Directive 96/61/EC was amended accordingly. Firstly the acceptable emission volumes are not set with reference to direct GHG emissions from installations subject to Directive 2003/87/EC. Secondly, member states may chose not to impose requirements on power efficiency if energy burning units or other units emit carbon dioxide on their premises without breaching any requirements, under Directive 96/61/EC. The European emission trading system is the first international cap-and-trade system applied at company level. The limit also called the “cap” is for some companies too small in face of their emission needs. This shortage allows for trading to development. The demand is generated by enterprises, which emit below the allocated limit and may sell the surplus at market price on the secondary market. Various instruments were used in Western Europe on the secondary market for emissions and price risk management9: • Spot contracts – offered by, inter alia, the exchange (Powernext, Nordpool, European Energy Exchange); • Futures – standardised contracts offered, inter alia, the exchange (primarily energy) ECX, Nordpool, EEX; • forward contracts – offered on the over the-counter market, OTC adapted to the needs of the parties involved. The key animators of this market are such investment banks as JP Morgan, Morgan Stanley, Barclays and chosen companies of corporations operating on the power and energy markets like Shell Trading; • Optional contracts – rarely applied instruments offered by other than exchange markets like banks and exchange (ECX); • Certifications of Emission Reduction (CER) units and Emission Reduction Units (ERU). Worldwide carbon dioxide emission trading was dominated from the start by trading on the European market thanks to the development in the European Union of an emission trading market. The global coal market in 2007 was valued at 40 billion Euro and constituted an increase by 80% as compared to 2006. The total volume 6 Vorschlag für eine Richtlinie des Europäischen Parlaments und des Rates über ein System für den Handel mit Treibhausgasemissionsberechtigungen in der Gemeinschaft und zur Änderung der Richtlinie 96/61/EG des Rates [KOM(2001) 581 endg. – Amtsblatt C 75 E vom 26.3.2002]. 7 Directive 2003/87/EC of the European Parliament and of the Council of 13 October 2003 establishing a scheme for greenhouse gas emission allowance trading within the Community and amending Council Directive 96/61/EC. 8 same, Preamble, paragraph 5. 9 Czarnecki P., Zarządzanie ryzykiem cen uprawnień do emisji dwutlenku węgla, Rynek Energii, 2007, no 5.

Andrzej Graczyk / Wrocław University of Economics

traded grew by 64% - from 1600 million Mg (1.6 billion ton equivalent of CO2) in 2006 to 2700 million Mg in the following year. The majority of the market is governed by EU ETS mechanisms – in 2007 1600 million Mg worth 28 billion Euro. This would mean volume growth by 62% and value increase by 55% as compared to 2006. At present EU ETS constitutes 62% of the global coal marker and 70% value of that market10.

THE SECOND STAGE OF MARKET DEVELOPMENT 2008–2012 The second stage of implementing the emission trading system overlaps with the first period of Kyoto protocol commitments where the allowance allocation method is uniform in all EU States. The participation of entities in identified sectors becomes mandatory. Member States allocate at least 90% of allowances free of charge starting from 1 January 2008 for a five year period. Every Member State develops a national scheme indicating the overall number of credits which it intends to distribute for that period and propose how they are to be allocated. The Scheme is subject to a consulting procedure and approval by the European Commission. In order to satisfy needs for emission allowances, companies may use credits acquired under the flexible mechanisms of the Kyoto Protocol. Today, allocation of allowances rules the market of emission trading deforming it before it began to develop. Unequal distribution of tradable credits based on transposing proportions from the previous period can be seen as unjustified public aid. A quota allocated free of charge disrupts the image of future credit demand because in the period of establishing allocation proportions no entity will reject the allocation and all protest that quotas are too small. Thus, it is difficult to assess the overall value of European market emission allowances. On one hand, it depends on the number of allowances, which entities will be capable of trading thanks to reducing their emission levels below this sum of acquired allowances. On the other, the market price, which can also influence the readiness of companies to reduce emission levels, will be decisive. The price of allowances for 2009 will depend on more than the fundamental factors. It will depend on the scale and persistence of the economic crises as well as steps undertaken by the US, EU and China to recover from the recession. At the beginning of 2009, the emission credit prices on the spot market (EU ETS) amounted to approximately 11 Euro per ton. Deutsche Bank forecasts that this year’s price for CO2 emission credits may drop to below 10 Euro11. Prices projected for the period up to 2012 may be adopted at the level of 20 Euro per ton. The price of 25–27 Euro is deemed less realistic (particularly in the years 2008–2009) due to the option of obtaining allowances from CDM12. The total market value may therefore be projected as a wide range estimation. On the basis of the number of credits issued in EU for 2079 million Mg emissions annually, and prices quoted above, market value is estimated at 20–40 billion Euro annually. The third stage of market development 2013–2020 Podstawą dalszego rozwoju rynku są dwie dyrektywy wchodzące w skład Pakietu energetyczno-klimatycznego: • The European Parliament and European Council Directive 2009/29/EC dated 23 April 2009 amending Directive 2003/87/EC to improve and extend the Community system for GHG emission credits13 (the so called EU ETS Directive) • The European Parliament and European Council Decision 2009/406/EC dated 23 April 2009 on efforts by Member States to reduce emission of greenhouse gasses to satisfy by 2020 Community commitments on reduction of GHG14 (the so called non ETS decision). The Community system (EU ETS) for emission trading today covers over half of CO2 emission and 40% of all emitted GHG. Therefore, the key instrument for reducing emission in the Community will be the EU ETS system. The emission volume covered by ETS is by 2020 to reach 21% of the projected reduction of allowances in the entire Union as compared to 2005, thus the admissible number of allowance in 2020 embraces 1720 million Mg CO2. 10 Roine K., Tvinnereim E., Hasselknippe H. (eds.), Carbon 2008 – Post – 2012 is now, Point Carbon, 11 March 2008, p.1, www.pointcarbon.com (enforced on 18.07.2008). 11 www.cire.pl/zielonaenergia/index.html?d_id=37778&d_typ=1 from 16.01.2009. 12 Majchrzak H., Krawczyk W., Wpływ uprawnień do emisji CO2 na cenę energii elektrycznej, Energetyka, 2008. 13 EU Official Journal 140/63 of 5.06.2009. 14 EU Official Journal 140/136 of 5.06.2009.

Development of CO2 emission trading in the european union

The remaining 60% of emitted greenhouse gasses will be covered by the provisions of the second key document, i.e. the non-ETS decision. The Decision projects a 10% reduction of greenhouse gasses emission in sectors not covered by EU ETS in the European Union as a whole (among others, transport, building, waste management and agriculture). The mechanism will be implemented in the entire European Union but Member States will remain competent to define their own policies in other economy sectors. The EU non-ETS reduction objective is diversified and some of the less prosperous Member States may even increase emission in the years 2013–202015. The EU ETS Directive projects auctioning as the basic method of allocating emission allowances. The total quantity of allowances to be auctioned by each Member State shall be made public by the European Commission by 31 December 2010. It shall be divided among Member States 88%/10%/2% accordingly, where: • 88% of the total quantity of allowances to be auctioned being distributed amongst Member States in shares that are identical to the share of verified emissions under the Community scheme for 2005 or the average of the period from 2005 to 2007, (whichever one is the highest) ; • 10% will be subject to redistribution based on GDP/per head criteria according to values specified in Annex IIa to the Directive. • 2% will be subject to redistribution based on reduction efforts up to date, according to values specified in Annex IIb to the Directive. Credit auctions are to be open, which means that every entity will have the opportunity to purchase credits in any EU country. Income from the sale of allowances will credit the budget of Member States. The European Commission estimates that the auction revenues in 2020 should amount to approximately 50 billion Euro16. The auction system will be introduced gradually, according to various criteria and methods depending on the economic sector17. The Directive divides the sectors covered by EU ETS into three groups: producers liable to emission leakage, producers of electric energy and other industry sectors, including heat production. An option for exemptions from the duty to buy auctioned credits for the power engineering sector was introduced for new Member States. The power engineerin sector will be entitled to receive part of their allowance free of charge on satisfying conditions specified in the Directive. The annual reduction quota for emission allowances will be reduced starting 2013 by 1.74%. The number of emission permits is assessed to be much lower than the projected emission volume. The lacking allowances will be available at auctions on the secondary market, to be purchased under the Kyoto Protocol mechanisms (or possibly from the next agreement that may be signed in December 2009 in Copenhagen) or from allowances acquired in the period 2008–201218. The circumstances described above mean that estimated economic effects of implementing the package are exceptionally difficult. The situation is further complicated by the economic crises, which on one hand reduces power demand causing a drop in prices of energy and falling prices of emission credits resulting from falling demand for credit purchase, and on the other leads to reducing industrial production and that in other industrial sectors. The European Commission estimates that the average price per ton of emitted CO2 may grow to approximately to 30–39 Euro in 2020. Some forecasts predict the price of even 80–100 Euro/Mg 202019.

PROJECTED MARKET DEVELOPMENT AFTER THE YEAR 2020 The development of the system for emission trading after 2020 is connected with adoption of an international agreement on reducing emissions globally. The Directive states that by 2050 global greenhouse gas emissions should drop by at least 50% below the level of 199020. The European Parliament also repeated the opinion that industrialised countries should make commitments to reduce greenhouse gas emissions by at least 30% by 2020 and by 60–80% by 2050 as compared to 1990. The European Union projects successful negotiations during the UN Climate Conference 2009 in Copenhagen (COP 15). Therefore, the Community should initiate development of more restrictive objectives in reducing emission for the year 2020 and the following years to 15 Poland, for example, may increase emission volume in the non-ETS sector by 14%. 16 Ibidem. 17 The system of allocating allowances free of charge will be based on indicators, which must be determined for particular sectors by the European Commission by the end of 2010. 18 Paczosa A., Błachowicz A., Jeszke R. et al., Zadania wynikające z nowych regulacji dotyczących redukcji emisji gazów cieplarnianych w Unii Europejskiej. Dyrektywa EU ETS & Decyzja NON ETS, Instytut Ochrony Środowiska, KASHUE, Warszawa, June 2009. 19 Stawski P., Wytwarzanie energii elektrycznej – uwarunkowania emisji CO2, Energetyka, 2008, No 12. 20 Preamble, paragraph 3.

Andrzej Graczyk / Wrocław University of Economics

ensure that after 2013 the Community system allows for a more stringent emission cap as the Communities’ contribution to the future agreement of climate changes21. It is projected that by 2020 the European system for emission trading will allow the EU to be successful in reducing emissions as planned in the Kyoto Protocol at costs below 0.1% of GDP. The system will also play a key role in implementing even more ambitious European goals in reducing emissions by 2020 and in the following years22.

SUMMARY The key idea underlining emission trading is that emitters whose costs of reducing emissions below the assigned limit are lower may lower their emission levels and sell extra emission allowances to other emitters (with higher emission costs). Thus, emission trading will automatically satisfy the conditions for minimising social costs of reaching the targeted emission cap. Emission reduction limits systematically grow. Their performance will satisfy Kyoto Protocol commitments in the period up to 2012. The development of the European emission trading system is embracing a growing number of entities and economic sectors. Market mechanisms keep improving and the flexible mechanisms of the Kyoto Protocol are introduced to the European system. Today, allocation of allowances rules the market of emission trading deforming it before it began to develop. Introduction of the auction system, starting 2013, eliminates this inconvenience and enforces competition between enterprises. The auction system should be governed by economic calculus based on various options for meeting the requirements on CO2 emission. Such flexibility ensures emission reduction in the most profitable manner for entrepreneurs, particular economic sectors, countries and the European Union in its entirety. Development of the emission trading market is thus a dynamic process. Wider application range and changing market forms will change the business environment of entities in various sectors, particularly in the energy sector.

21 Same, paragraph 4. 22 EU counteracting climate change. European Emission Trading Scheme, Office for Official Publications of the European Communities, Luxembourg 2008.

Development of CO2 emission trading in the european union

LITERATURE 1. Czarnecki P., Zarządzanie ryzykiem cen uprawnień do emisji dwutlenku węgla, Rynek Energii, 2007, nr 5. 2. Decyzja Parlamentu Europejskiego i Rady 2009/406/WE z dnia 23 kwietnia 2009 r. w sprawie wysiłków podjętych przez państwa członkowskie, zmierzających do zmniejszenia emisji gazów cieplarnianych w celu realizacji do roku 2020 zobowiązań Wspólnoty dotyczących redukcji emisji gazów cieplarnianych, Dziennik Urzędowy Unii Europejskiej L 140/136 z 5.06.2009. 3. Dyrektywa 2003/87/WE Parlamentu Europejskiego i Rady z dnia 13 października 2003 r. ustanawiająca system handlu przydziałami emisji gazów cieplarnianych we Wspólnocie oraz zmieniająca dyrektywę Rady 96/61/WE, Dziennik Urzędowy Unii Europejskiej L 275/32 z 25.10.2003. 4. Dyrektywa Parlamentu Europejskiego i Rady 2009/29/WE z dnia 23 kwietnia 2009 r. zmieniająca Dyrektywę 2003/87/ WE w celu usprawnienia i rozszerzenia wspólnotowego systemu handlu uprawnieniami do emisji gazów cieplarnianych, Dziennik Urzędowy Unii Europejskiej L 140/63 z 5.06.2009. 5. Działania UE przeciw zmianom klimatu. Europejski System Handlu Emisjami (ETS), Urząd Oficjalnych Publikacji Wspólnot Europejskich, Luksemburg 2008. 6. Fiedor B., Graczyk A., Jakubczyk Z., Rynek pozwoleń na emisję zanieczyszczeń na przykładzie SO2 w energetyce polskiej, Wydawnictwo Ekonomia i Środowisko, Białystok 2002. 7. Majchrzak H., Krawczyk W., Wpływ uprawnień do emisji CO2 na cenę energii elektrycznej, Energetyka, 2008, nr 10. 8. Paczosa A., Błachowicz A., Jeszke R. i wsp., Zadania wynikające z nowych regulacji dotyczących redukcji emisji gazów cieplarnianych w Unii Europejskiej. Dyrektywa EU ETS & Decyzja NON ETS, Instytut Ochrony Środowiska, KASHUE, Warszawa czerwiec 2009. 9. Protokół do Ramowej konwencji Narodów Zjednoczonych w sprawie zmian klimatu, Dz.U. nr 203 poz. 1684 z dnia 17 października 2005. 10. Roine K., Tvinnereim E., Hasselknippe H. (eds.), Carbon 2008 – Post – 2012 is now, Point Carbon, 11 March 2008, s. 1, [dokument internetowy, kod dostępu: www.pointcarbon.com]. 11. Stawski P., Wytwarzanie energii elektrycznej – uwarunkowania emisji CO2, Energetyka, 2008, nr 12. 12. Vorschlag für eine Richtlinie des Europäischen Parlaments und des Rates über ein System für den Handel mit Treibhausgasemissionsberechtigungen in der Gemeinschaft und zur Änderung der Richtlinie 96/61/EG des Rates [KOM(2001) 581 endg. – Amtsblatt C 75 E vom 26.3.2002].

Jacek Klucznik; Robert Małkowski / Gdansk University of Technology Piotr Szczeciński; Ryszard Zajczyk / Gdansk University of Technology Authors / Biographies

Jacek Klucznik Gdańsk / Polska

Robert Małkowski Gdańsk / Polska

He graduated from the Faculty of Electrical Engineering and Automation of Gdańsk University of Technology in 1999. Five years later he got his PhD. He works as an assistant professor in the Chair of Electrical Engineering of Gdańsk University of Technology. He deals with regulation systems of generators and turbines, wind power engineering and electrical engineering protection automation.

He graduated from the Faculty of Electrical Engineering and Automation of Gdańsk University of Technology in 1999. Four years later he got his PhD. He works as an assistant professor in the Chair of Electrical Engineering of Gdańsk University of Technology. His scientific interest focus on wind energy issues, critical electrical energy systems failures, as well as on levels of voltage and reactive power distribution in electric power systems.

Piotr Szczeciński Gdańsk / Polska

Ryszard Zajczyk Gdańsk / Polska

He graduated from the Faculty of Electrical Engineering and Automation of Gdańsk University of Technology and was awarded Master’s degree in electrical engineering. He worked in the Institute of Power Engineering Gdańsk Branch for five years and then came back to his University, where he pursues his interests in direct current energy transmission, electrical power system stability, excitation systems and FACTS type of systems.

He was awarded Master’s degree in the Faculty of Electrical Engineering of Gdańsk University of Technology in 1978, PhD – in 1988, second level doctorate (habilitation) - in 1997, and became full professor in 2004. He works in the Chair of Electrical Power Engineering of Gdańsk University of Technology as a professor and is the head of the chair. His scientific interests focus on electrical power and power systems, and electrical engineering automation.

Conditions favouring voltage collapse in the operation of generator regulators – selected issues

CONDITIONS FAVOURING VOLTAGE COLLAPSE IN THE OPERATION OF GENERATOR REGULATORS – SELECTED ISSUES

           Jacek Klucznik / Gdansk University of Technology  Robert Małkowski / Gdansk University of Technology  Piotr Szczeciński / Gdansk University of Technology  Ryszard Zajczyk / Gdansk University of Technology   

1. INTRODUCTION  Generator regulator structures applied today and the presettings of main circuits of voltage regulators         primarily affect voltage regulation rate and local stability. Signals from the regulation system, relating to the  limitation of the synchronous generator field of action, play the key role in excitation control in hazardous     from       structure is equipped with: situations resulting low or high voltage. Every regulator apart from its inherent          • underexcitation limiter, named also limiter of power factor angle [OKM]  • excitation minimal current limiter of generator [OMPW]   •  induction limiter V/Hz [OI]  •  excitation current limiter of generator [OPW]  •  stator current limiter of generator [OPS]  •  overvoltage limiter [ONN]. 

   A structural diagram of a multiparameter generator regulator for machine excitation  diode  in  exciter and excitation rectifier) is presented Fig.1.             

           Fig. 1. Structural diagram of multiparameter generator regulator for machine excitation systems [1]

Abstrtact  The paper focuses on selected issues relating to the operation of multiparameter generator regulators in voltage collapse. Results of studies are presented regarding the influence of the system stabiliser, a component of the generator regulator system so often neglected. Attention is brought to the advisability of automating the process of active power decreasing in increasing the capacity for reactive power generation. Furthermore, the paper indicates errors in the structure of the primary circuit for voltage regulation with the LV and HV gates intercepting signals in the system.

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systems (with AC

Jacek Klucznik; Robert Małkowski / Gdansk University of Technology

   ee     e  Piotr Szczeciński; Ryszard Zajczyk / Gdansk University of Technology eeeee    ee     e 

eeeee  2. IMPACT ANALYSIS OF PRESENT STRUCTURE, ACTING ALGORITHMS AND PRESETTING OF  POWER SYSTEM STABILIZER (PSS) ON POTENTIAL VOLTAGE FAILURE AND RESULTANT COURSE         OF EVENTS                      2.1. Introduction                electromechanical      The excitation control system, increasing swinging damping, is called a system   stabilizer, most often marked with the acronym PSS (Power System Stabilizer). The system, apart from limiters,        constitutes an integral part of generator regulators used today.                 single   We  System stabilizers can  be classified  according to thenumber of input signals. can identify     contain           input and  multi-input stabilizers. Stabilizer input signals or signal should information on the possible               electromechanical swinging. Single-input stabilizers apply angular velocity of synchronous generator rotor,                       1 active power generated or voltage frequency on generator terminals. Multi-input system stabilizers use two   input signals. The most common systems used are those applying measuring generator shaft rpm or generator               active power. The general structure of a single input system stabilizer is shown in Fig. 2, whereas a 2-input type                       system stabilizer is given in Fig. 3.                    

             

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                          

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 

 

  



Fig. 2. Structural diagram of 1-input system stabilizer

                                                    



  



    

    



  

     

    

    

         

    

 

   

 

     

     

     

     



   

       



                                 Fig. 3. Structural diagram of 2-input system stabilizer of PSS2B type  [4]          

     structures:   and       A  series of analysis was made for two NES used system stabilizers 1-input 2-input, to            identify the relations between parameters of stabilizers and the system’s contribution to the loss of generator         stability in terms of voltage collapse.         Analysis of system stabilizers’ in conditions favouring the initiation of voltage collapse has     operation          demonstrated that stabilizer structure, amplification factor and values of input limits are of key significance. In         some cases, operation of system stabilizers can be disadvantageous in terms of ensuring voltage stability. The   problem can be explained by the fact that system stabilizers act in transient states when values of stabilizer    input signals change. In synchronous generators equipped with a 1-input type system stabilizer, relying on measurement of active power, the functioning of system stabilizers is visible when the value of generated  active power  fluctuates.

This is the most commonly applied solution in generation units operating in NES [National Electrical System]

Vg [-]



Vg [-]

             Conditions  favouring collapse  in the operation of  generator regulators –       voltage     selected issues 51                                  Variations of generator active power can be generated by the following two factors:   –      in the    • external such as short-circuits or violent voltage instability power system,   occur            • internal – related with the turbine regulation system, when variations of turbine mechanical power          in result of activated primary or secondary regulation or with malfunctions  related with boiler  operation.            If during external disturbances system stabilizers function correctly, increasing the damping of      from  electromechanical swinging,  we can observe phenomena, resulting turbine  power instability, that may               contribute to voltage collapse.    dPg  2  < 0 ,  When the decreases output signal of the stabilizer is positive  U    generation          > 0  the          stab  dt    increased excitation voltage and in effect generatorvoltage. Such a  situation does not generate a resulting    in        dPg      risk for  loss of voltage stability. The situation can become worse with increasing  turbine power, when dt > 0            < 0. The and stabilizer signal  has a negative value U stabilizer added to the voltage error of primary    signal stab     circuit regulator results indipping both excitation voltage as well as generator voltage.                   2.2. Exemplary results of simulation studies e An example of the operation referred to above is presented in Fig. 4a. The simulatione was performed in a  one-machine system for 235MVA turbo-set, equipped with a machine excitation system. The amplification factor              e of the system stabilizer varied, taking 50%, 100% and 200% of the base value, corresponding to the markings in            Fig. 4a.  (k = 0.5, k =  1 and k = 2).               In an extremely adverse situation, the  system stabilizer can generate a signal, resulting from stabilizer          , VSmax, at the level of – 0.05÷0.09. Therefore, in  the worst case the stabilizer can cause a drop in limits V    Smin   generator voltage of about 0.05, which coinciding with dipping generator voltage can pose the risk of voltage   collapse. To counteract the above, the system stabilizer limiter should be set unsymmetrical VS max  > VS min to        stabilizer      the       the limit excessive fall of generator voltage. Another option for restricting output signal involves      reduction of the stabilizer amplification factor, but this leads to decreased operational efficiency of the system                      stabilizer.               b)      a)                          k = 2               k = 1 k = 0.5 k = 1 k = 0.5 k=2             1.001  1.005                        1 1      0.995        0.999     0.99 0.998     0.985 0.997      0.98 0.996      0.975 0.995             0 10 20 30 0 10 t [s] 20  30 t [s]      PSS na  Rys.wartości 4. Wpływ wartości współczynnika wzmocnienia PSS  na przebieg napięcia Rys. 4. Wpływ współczynnika wzmocnienia przebieg napięcia generatora przy skokowej zmianie generatora mocy zadanej turbozespołu;     zadanej    jednowejściowy, b) a) stabilizator jednowejściowy, b) stabilizator dwuwejściowy przy skokowej zmianie mocy turbozespołu; a) stabilizator stabilizator dwuwejściowy  Two-input stabilizers, basing on measurement of generator active power and its stator rpm, are free of the

resulting from power instability3. defect involving generation of a na non-grounded signal U > 0wyjściowego Wady, polegającej generowaniu input niezerowego V pssturbine > 0 przy pss    sygnału  Inzmianach effect, no voltage error appears with turbine power changes. curves dwuwej ściowe,The bazuj ące napresented pomiarze in Fig. 4b show mocy turbiny, pozbawione są stabilizatory          3 system stabilizer. In effect, there that turbine power variations lead to a very small output signal from the mocy czynnej generatora i prędkości obrotowej wirnika generatora . Dzięki temu nie     powoduj        power is in practice no voltage dipping on generator with increasing of the generating unit, thus ą one powstawania uchybu napięciaterminals przy zmianach mocy turbiny. Przedstawione na  eliminating the great defect of 1-input stabilizers basing on the measurement of generator active power. rysunku 4b przebiegi wskazują, Ŝe zmiany mocy turbiny powodują powstawanie bardzo         niewielkiego sygnału wyjś ciowego stabilizatora systemowego. Dzi ęki temu przy zwiększaniu 2 The amplification factor is negative, causing inversion of input signal phase by 180º.  mocy jednostki wytwórczych praktycznie nie dochodzi do obniŜania napięcia na zaciskach 3 Today NES applies voltage frequency measurement of generator in place of the rpm measurement, however this does not alter the principle of generatora, co  było główną wad stabilizatora jednowej ściowego bazującego na pomiarze   ą   stabilizer operation mocy czynnej generatora.          

Jacek Klucznik; Robert Małkowski / Gdansk University of Technology Piotr Szczeciński; Ryszard Zajczyk / Gdansk University of Technology

2.3. Conclusions The conducted analysis pointed to the following conclusions: • Single-input system stabilizers, with measurement of active power, can lead to dipping generator voltage in result of turbine power instability. The voltage decrease depends on stabilizers presettings – amplification factor and limiters of input signal. We can assume, on the basis of selected stabilizer presettings used in NES that maximum voltage decrease in the effect of stabilizer operation can achieve 5%. This value, in case of extremely unfavourable voltage values, can put stability at risk. The problem can be solved by locking decreasing block power in case of dipping voltage, what is also advantageous from the point of view of 4 . Dobór nastaw nowopowstających i modernizowanych blokach tego typu układów stator current limiter. Another solution is the usage of 2-input stabilizers, where problems with takich voltage error stabilizatorów musi4 odbywać sięnever indywidualnie dla kaŜdego z bloków z uwzględnieniem in turbine power instability practically occur. 4 nowopowstających i modernizowanych blokach tego typu układów . Dobór nastaw takich .stabilizers Dobór nastaw takich nizowanych• blokach tego typu układów stabilizatorów musi odbywać się indywidualnie dla this kaŜdego zmoŜna bloków z uwzględnieniem No ich impact of two-input on potential voltage failure is observed. Thus, of installation specyfiki, sposobu powiązania z systemem elektroenergetycznym itp. Nietype w ich specyfiki, sposobu powiązania z systemem elektroenergetycznym itp. Nie moŜna w 4 ać się indywidualnie dla każdego z bloków z uwzględnieniem . Presettings selection of stabilizers should be done is proposed on all newly and modernized sposób ogólny podaćbuilt zalecanych nastaw,blocks zaleŜą one od efektów, które ma powodować sposób ogólny podać zalecanych nastaw, zaleŜą one od efektów, które ma powodować iązania z systemem elektroenergetycznym itp. Nieinto można w stabilizator individually for each block taking consideration its specifics, connection to the power system, etc. w odniesieniu do danego generatora (kołysania własne) stabilizator w odniesieniu do danego elektroenergetycznego generatora (kołysania (kołysania własne) i systemu i systemu obszarowe i międzyobszarowe). anych nastaw, zależą one recommendations od efektów, które should ma powodować Presetting not be generalised as the presettings depend on the stabilizer’s effects elektroenergetycznego (kołysania obszarowe i międzyobszarowe). u do danego on generatora (kołysania własne) i power systemu the generator (own swinging) and system (area and inter-area swinging). 3. Zasady odciąŜania turbin w celu zwiększenia generacji mocy biernej

ysania obszarowe i międzyobszarowe).

3.1 Wstęp

Wartość mocy biernej generowanej przez generator synchroniczny, jest nierozerwalnie 3. Zasady odciąŜania turbin w celu zwiększenia generacji mocy biernej związana z wartościąREACTIVE napięcia generatora. Ograniczeniem generowanej przez generator 3. PRINCIPLES OF TURBINES UNLOADING TO INCREASE POWER GENERATION w celu zwiększenia generacji mocy biernej synchroniczny mocy biernej jest wartość dopuszczalna prądu stojana i prądu wzbudzenia. 3.1 Wstęp Definicja ograniczeń opisanych zaleŜnościami (1) i (2) pozwala na wyznaczenie obszaru 3.1. Introduction dopuszczalnej pracy na płaszczyźnie P-Q, co pokazano na rys. 5. Wartość mocy biernejingenerowanej generator synchroniczny, nierozerwalnie Reactive power, generated synchronous przez generators, is inseparably relatedjest to the generator voltage. + Q ≤ S = (V × I ) enerowanej przez generatorz synchroniczny, jest nierozerwalnie związana wartością napięcia generatora.P Ograniczeniem generowanej przez generator (1) 2 g

2 g

The admissible value of stator and excitation currents is limited by the generated reactive power from the syna generatora. Ograniczeniem generowanej generator synchroniczny biernejprzez jest wartość dopuszczalna stojana prądu wzbudzenia. chronous generator.mocy The definition of limits delineated by and (2)iidentifies the area of permit the × V  (1) V relations  V prądu ≤  P +  Q + est wartość ted dopuszczalna prądu stojana i prądu wzbudzenia.  xpozwala  (2) operation on plane P-Q,opisanych which is presented in Fig. 5. x Definicja ograniczeń zaleŜnościami (1) i na wyznaczenie obszaru (2)     h zależnościami (1) i (2) pozwala na wyznaczenie obszaru dopuszczalnej pracy na płaszczyźnie P-Q, co pokazano na rys. 5. yźnie P-Q, co pokazano na rys. 5. 

2 g

P + Q ≤ S = (Vg × I gM ) 2 g

2 g

 2 Vg2   Vg × V fM ≤ P +  Qg +   x x d  d   2 g

2 g



2 g

(1)

  

(1)

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  

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Rys. 5. Obszar

     



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 stanów   dopuszczalnych









pracy generatora synchronicznego przy napięciu

Fig. 5. The area of admissible synchronous generator operation states at rated voltage (continuous lines) and at voltage less than rated (intermittent znamionowym (linie ciągłe) i przy napięciu mniejszym do znamionowego (linie przerywane).  limit (1)(current) – granicalimit wynikająca z dopuszczalnej obciąŜalności prądowej stojana, by (2)stability – granica lines). (1) – admissible stator ampacity limit , (2) – admissible voltage of excitation, (3) – natural balance (conditioned wynikająca z dopuszczalnego napięcia (prądu) wzbudzenia, (3) – granica równowagi requirement). To simplify the figure only limits resulting from admissible current of machine rotor and stator are presented. naturalnej (wynikająca z warunku zachowania stabilności). Dla uproszczenia na rysunku

When the value of generated reactive power Postulat is too high, i.e. exceeds the generator permitted operation ten jest zgodny z zapisami w IRiESP [6] area, the generator regulator changes operational priorities, from voltage regulationto operation with quasi fixed value of stator or rotor current. In such circumstances systems called rotor current limiters or stator current limiters reduce the generator excitation voltage reducing the excitation current (rotor current) and generator voltage reducing the generator stator current according to Formula (1). Enhancing the generating possibilities of reactive power range is important particularly in case of low generator voltage. In result of low voltage, stator current increases as well as the generated  active power Pg1. Reduction of reactive power is necessary to prevent overheating of stator windings. This is illustrated in Fig. 5,             where the generated reactive power must be lowered from Qg1 to Qg2 following lower generator voltage from   Vg1 to Vg2 to keep the generator in the acceptable range. The problem grows if a permanent reactive power deficiency occurs. synchronicznego przy napięciu ch stanów pracy generatora  Another current limitation method is to decrease active power generation. The decreasing of active rzy napięciu mniejszym dostator znamionowego (linie przerywane). opuszczalnej obciążalności prądowej stojana, (2) stanów – granicapracy generatora synchronicznego przy napięciu Rys. 5. Obszar dopuszczalnych napięcia (prądu) wzbudzenia, (3) – granica równowagi 4 This proposal complies with IRiESP (Instrukcja ruchu i eksploatacji sieci przesyłowej) notations [Electrical Power Transmission Network znamionowym (linie ciągłe) i przy napięciu mniejszym do znamionowego (linie przerywane). Running and Operating Instructions] [6]. unku zachowania stabilności). Dla uproszczenia na rysunku

w IRiESP [6]

(1) – granica wynikająca z dopuszczalnej obciąŜalności prądowej stojana, (2) – granica wynikająca z dopuszczalnego napięcia (prądu) wzbudzenia, (3) – granica równowagi naturalnej (wynikająca z warunku zachowania stabilności). Dla uproszczenia na rysunku

Conditions favouring voltage collapse in the operation of generator regulators – selected issues

power generation from Pg1 to Pg2 increases potential reactive power generation in each case. Reactive power generation can decrease to Qg3, i.e. by ∆Qg. In case of reactive power generation deficit, possible reactive power generation growth is a desirable feature. To recapitulate, by decreasing active power we can increase the generated reactive power, within admissible stator current limits, without decreasing generator voltage. The solution was mentioned in a paper on voltage collapse of 26-th June 2006 [2], however, the problem was not extensively discussed.

3.2. Examples of simulation study results Today, generator unloading as a preventive measure against generator overloading in case of voltage collapse risk is described in emergency procedures. The only drawback of such unloading is its manual character at dispatcher’s command. Results of simulation studies for automatic generator unloading are presented below. Dipping voltage and appearance of reactive power swinging in result of limiters reaction of power angle and stator current5 triggered the procedure of generator unloading. The first stage of unloading was activated directly following disclosure of “inter-forcing” of limiters (acting OPS, OKM and reactive power swinging). The following two stages are activated after a specified interval, provided the conditions for stage 1 are met. Unloading power in the following stages was 5% Pgn. Professional literature refers to various conditions required to initiate the process of automatic unloading. These involve either voltage level or delay or reactive power close to zero at activated power angle limiter. Constant values of delay and voltage presettings can be a defect in the first case, while in the second case the defect may involve negligence of dynamic alteration of activation limit for OKM depending on voltage and no reversal of OPS sign). The proposed solution does not feature the level (OKM activation at QogrOKM > 0,  defect. Results of simulator study examples for a  case of dynamic Qogr = f(Vg),  Fig.7,  and constant limit       value OKM, (Fig. 6.) confirm the above.           

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                          Fig. 6. Effects of generator unloading operation, taking into account the sign of reactive power in OPS. Regulator structure – correction: a) generator  c)    power,    voltage, b) excitation current, generator current, d) generator reactive power,  e) generator active f) signals form individual limiters. OGR – overall signal.  

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 Problems resulting from inter-forcing of limiters are elaborated in [5].                        

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             Jacek Klucznik; Robert Małkowski / Gdansk University of Technology              Piotr Szczeciński; Ryszard Zajczyk / Gdansk University of Technology               Not all structures of power angle limiters (OKM) take into account the influence of generator voltage.  However, voltage value on generator bus-bars has a significant impact on the value of the stability limit (falling   voltage results in limit displacement to point of inductive power, see: Fig. 5, curves 3). The power angle limiter           should change the limitation position depending on voltage value. Results obtained for the case shown in Fig.             6 are presented below, however, in this case the impact of changing limitation level, initiated by alternating           voltage on generator terminals is taken into account.  

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             Fig. 7. Effects of generator unloading taking into account the sign of reactive power in OPS. Regulator structure – corrective accounting for dynamic    active power, variation of QogrOKM = f(Vg): a) generator voltage, b) excitation current, c) generator current, d) generator reactive power, e) generator f) signals from individual limiters. OGR – overall signal.   3.3. Conclusions from simulation studies The  following conclusions are drawn from the simulation study results: • Generator unloading by alteration of generator active power presetting value increases the generator volt age stability margin in case of voltage collapse. Automation of the process is desirable. The criterion referred to in the paper can be applied for this purpose– individually or jointly with other criteria.  • Active power limiters should be above all installed in blocks, which are most susceptible to voltage collapse.  • Active power decreasing for generating blocks is pointless, if the limitation of reactive power generation is            not caused by generator regulator systems, but by ARNE system. Therefore, correct presettings of reactive         power limiters in ARNE systems should be reviewed.          • Dynamic alternating of reactive power limit Q = f(Vg)  in OKM is necessary. into account the  generaogr       Taking  tor ‘s actual voltage level facilitates effective protection of the generator against stability loss (compare Fig.  6 and Fig. 7)                                                                        

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4 Wpływ lokalizacji bramek wybierających sygnał w głównym torze układu Conditions favouring voltage collapse in the operation of generator regulators – regulacji napięcia na przebieg awarii napięciowej selected issues    e e    e  4.1 Wstęp eeee

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4. IMPACT SIGNAL SELECTION GATES POSITIONING IN THE PRIMARY VOLTAGE W OF układach analogowych i cyfrowych w głównym torze regulacji stosuje CIRCUIT się z reguły REGULATION SYSTEMjako ONwzmacniacza VOLTAGE FAILURE SEQUENCE strukturę regulatora, ze sprzężeniem korekcyjnym, rys. 1.   

Jedną z różnic w spotykanych w KSE układach analogowych i cyfrowych jest sposób  4.1. Introduction wprowadzania sygnałów z ograniczników do toru głównego regulacji.  As a  rule, regulator structure is applied as a correction coupling amplifier (Fig.W1), układach in digital and analogue analogowych sygnały ograniczników wprowadzane są do węzłów sumacyjnych przed lub za           systems in the primary regulation circuit. wzmacniaczem z członem korekcyjnym. W stosowanych obecnie cyfrowych układach  One of the differences between digital and analogue systems in NES is the method of signal input from liwzbudzenia stosuje się wprowadzenie ograniczników poprzez bramki przejmujące        miters to the primary regulation circuit. In sygnałów analogue systems limiters signals feed the summing junction before  sygnały LV i HV. Wprowadzenie przez jeden z ograniczników do bramki LV wartości or after the correction coupling amplifier unit. Contemporary digital excitation systems feed the limiter signals            mniejszej od sygnału z głównego  toru regulacji jest jednoznaczne z przejęciem regulacji through gates accepting LVand HV signals. The access a signal below the primary regulation circuit to LV       of    wzbudzenia przez sygnał z ogranicznika. Wprowadzenie do bramkiHV sygnałów większych gate through one of limiters is synonymous with the signal from the limiter intercepting excitation regulation. od sygnału z toru głównego regulacji, powoduje przejęcie regulacji wzbudzenia przez sygnały Input of signals to HV gate over the primary regulation circuit signals results in signals from those limiters z tych ograniczników. Przy niepobudzonych ogranicznikach sygnał z ograniczników takingover control. In the case of inactivated limiters, their signalinput to LV gate is 10V, and on HV excitation    wchodzący na bramki LV  wynosi 10V, a na bramkę HV odpowiednio 0V.  gate 0V, respectively.  Przykładową strukturę stosowanych regulatorów przedstawiono na rys. 8. Stosowane An example of regulator structure is presented in Fig. 8. The applied solutions of limiters’ signal input to          rozwiązania z wprowadzaniem sygnałów z ograniczników do węzłów sumacyjnych przed lub  summing junctions before or after the correction amplifier unit, can be met in technologically older excitation zawzmacniaczem korekcyjnym, można spotkać w starszych technologicznie  z członem     systems. układach wzbudzenia. 

 diagram          regulation systems. Fig. 8.Rys. Block of primary circuit for voltage applied by domestic and foreign producersof automatic voltage 8. Schemat blokowy toru regulation głównego regulacji napięcia stosowany u krajowych i 

zagranicznych producentów układów automatycznej regulacji napięcia. The presently applied digital systems of generators’ regulation, in which regulation algorithms take into          consideration gates intercepting signals, do not require additional system locking limiters, as in the case of Obecnie stosowane cyfrowe układy regulacji generatorów, których algorytmy regulacji  older, power angle and stator current analogue systems for generator regulation. The priority of the control uwzględniają stosowanie bramek przejmujących sygnał, nie wymagają dodatkowych układów             signal in digital systems is defined by the position of the gate intercepting control signals. According to Fig. 8, blokujących ograniczniki, jak to jest w ogranicznikach kąta mocy i ogranicznikach prądu         the stojana signal is w fedstarszych, from the power angle limiter to theregulacji HV gate secondary to the LV gate.  In effect, analogowych układach generatorów. Nadrzędność sygnałuthe signal from         the sterowania power anglewlimiter (OKM) is secondary output from the limiter of excitation current (OPW) and układach cyfrowych jesttodefiniowana kolejnością rozmieszczenia bramek       signals         (OPS).    kąta   sygnały sterujące. Zgodnie z rys. 8 sygnał z ogranicznika mocy jest fromprzejmujących the limiter of  stator current           wprowadzany do bramki HV, podrzędnej względem bramki LV. Powoduje to, że sygnał z  kąta mocy (OKM) 4.2.ogranicznika Results of simulation studiesjest podrzędny względem sygnałów z ogranicznika prądu wzbudzenia (OPW) i z ogranicznika prądu stojana (OPS).  Figures 9, 11, 13 and 15 show the curves of active and reactive power, generator current and voltage, excitation voltage and current and signals from individual limiters in the case of dipping voltage in the power  supply system to 370 kV in the structure shown in Fig. 8. Dipping voltage in electric power systems with proper4.2 Wyniki badań  ly operating limiters insymulacyjnych the structure, shown in Fig. 8, reduce the voltage of synchronous generator excitation           and may, inNasome result loss of generator synchronism. Dipping voltage in power activate rys. cases, 9, 11, 13 i 15inprzedstawiono przebiegi mocy czynnej i mocy biernej, prądusystems i the napięcia excitation generatora, current limiter and later limiter and limiter, (Fig. 15). Repeated napięcia i stator prądu current wzbudzenia orazexcitation sygnały current z poszczególnych activation of excitation current limiter results in de-excitation of the synchronous generator and its falling out  9 of step. As presented in Fig. 15, the operation of the stator current limiter, in terms of reactive power consumption and power angle limiter, do not influence the generator regulator system in result of signals flowing from both limiters to the secondary gate. Incorrect positioning of signal intercepting gates intercept the signal in the primary regulation circuit, the high signal input from the power angle limiter to the HV gate cannot take over control. Operation of the minimum current excitation limiter in this case is too slow, because excitation current reaches the maximum value when excitation voltage falls to zero, Fig. 13. Minimum current excitation limiter traces the value of the excitation current but that limiter is activated too late, practically after falling out of step. Structure alteration of the primary regulation circuit, which involves a change in sequence of gates intercepting signals of LV to HV limiters, results in the power angle limiter taking over control of the signal. The signal from the power angle limiter and stator current limiter in terms of reactive current consumption will be,

                       Jacek Klucznik; Robert Małkowski / Gdansk University of Technology          Piotr Szczeciński; Ryszard Zajczyk / Gdansk University of Technology                        in this case, primary signals. Figures 10, 12 and 14, 16 present active and reactive power curves, generator  current and voltage, excitation voltage and current and also signals from individual limiters in the case of dipping voltage electric power system  to 370 kV,for generator regulator system with altered structure of main  in        circuit, shown in Fig. 17 .            

  Fig. 9. Curves of active and reactive power at slow electric power    voltage reduction below  370 kV       

       Fig. 10. Curves of active and reactive power at slow electric power      voltage reduction below 370 kV. Change in LV HV gate sequence       

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       Fig. 11. Curves of voltage and current of synchronous generator at    slow electric power voltage reduction below 370  kV          

 Fig. 12. Curves of voltage and current of synchronous generator at   slow electric power voltage reduction below 370 kV. Change in LV HV gate sequence            

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                Fig. 13. Curves of excitation voltage and current of  synchronous       generator at slow electric power voltage reduction below 370 kV            

                     Fig. of control signals in voltage regulator at slow electric 14.Curves      power voltage reduction below 370 kV.  Change in LV HV gate sequence                



Fig. 15. Curves of control signals in voltage regulator at slow electric           power voltage reduction below 370 kV Fig. 16. Curves of excitation voltage and synchronous generator      current  at slow electric power voltage reduction below 370 kV. Change      in      LV HV gate sequence      

                    The change of gate sequence provides protection of the synchronous generator against falling out of          step. According to Fig. 16, the excitation current limiter is the first to react to voltage dipping, and is followed        the by the stator current limiter, and the superior signal of power angle limiter takes control and becomes     over    superior control signal. Change of gate positions allows for compliance with design assumptions of analogue   excitation systems.                                               

          Conditions favouring voltage collapse in the operation of generator regulators –              selected issues            RA – regulacja automatyczna

Ograniczniki:

UNast Ug -

1+sTA 1+sTB

1+sTC 1+sTD

OKM [V] OPW [V]

RR – regulacja ręczna

IfNast Ifg -

Nastawy:

OKM [V]

0-10 [V]

OPW [V]

0-10 [V], I2t [A2s]

OPS [V]

0-10 [V], I2t [A2s]

OPS [V] KIA

1+sTIA 1+sTIB

LV GATE

RR RA – regulacja automatyczna RR – regulacja ręczna

HV GATE

Ust

           Fig. 17. Correct sequence of gates selecting the signal in the primary voltage regulation circuit 



 4.3. Conclusions In new, contemporary digital generator regulation systems, the sequence of gates selecting signals in  the primary regulator circuit conform to the standard [4]. According to the standard and in the some digital generator regulation systems, the sequence of gates selecting signals follows the pattern in Fig. 7 (HV gate; LV gate). Gates thus positioned select the signal from limiters of stator and rotor currents as the superior si a structure is gnal. The signal of the power angle limiter entering the first gate selects the higher signal. Such  inadmissible and in states of low voltage reduces the exciting voltage of the synchronous generator by current limiters, signals of which feed the second gate, selecting the lower signal value. In such a structure of primary voltage regulation circuit, the last element of the circuit is superior in the regulation system; which does not conform to the precursors’ assumptions for analogue systems. 5. SUMMARY An extensive analysis of generator regulator operations indicates the hazards relating to seemingly known structures of synchronous generators regulation systems. In conditions of dipping voltage, a malfunctioning generator regulator can cause a voltage collapse or augmented consequences. Elimination of risks described in the article will significantly improve electric power system operational safety.

LITERATURE 1. Zajczyk R., Modele matematyczne systemu elektroenergetycznego do badania elektromechanicznych stanów nieustalonych i procesów regulacyjnych, Wydawnictwo Politechniki Gdańskiej, Gdańsk 2003. 2. Madajewski K., Sobczak B., Trębski R., Praca ograniczników w układach regulacji generatorów synchronicznych w warunkach niskich napięć w systemie elektroenergetycznym, materiały konferencyjne APE ’07, Gdańsk 2007. 3. Kundur P., Power system stability and control, McGraw-Hill 1994. 4. IEEE Std 421.5 – 2005 IEEE Recommended Practice for Excitation System Models for Power System Stability Studies. 5. Analiza stanu obecnego i opracowanie zmian w układach regulacji napięcia i mocy biernej w elektrowniach, stacjach sieci przesyłowej i w sieciach rozdzielczych w celu zmniejszenia ryzyka powstania awarii napięciowych w systemie elektroenergetycznym. Etap II, praca badawczo-rozwojowa wykonana dla PSE-Operator SA. 6. IRiESP – Warunki korzystania, prowadzenia ruchu, eksploatacji i planowania rozwoju sieci v. 1.2. Tekst jednolity obowiązujący od dnia: 5 listopada 2007 roku.

Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A. Authors / Biographies

Jerzy Kulczycki Kraków / Poland

Michał Rudziński Kraków / Poland

Graduate of Silesian University of Technology in Gliwice (1956). He was awarded PhD in AGH University of Science and Technology in Kraków (1967), then, in 1976 - second level doctorate (habilitation) and became a professor in 1991. During the period of 1956–72 he worked mainly at installment and project design of electrical power systems. Since 1972 – an academic teacher in AGH University of Science and Technology. His professional interests include electrical power engineering, in particular, methods of designing optimum system structures, enhanced efficiency of using of electrical power systems.

Graduate of the Faculty of Faculty of Electrical Engineering, Automatics and Electronics of AGH University of Science and Technology in Kraków. He was awarded Master’s – engineer’s degree in electrical automation and metrology in 1979. During the period of 1979– 1983 he worked in Kielce in research and development center of industrial fittings (Ośrodek Badawczo-Rozwojowy Armatury Przemysłowej). During the period of 1983–1995 he was employed in T. Sendzimir steelworks in Kraków as a specialist in Power Engineering Division. Since 1995 he as been working in electrical power distribution company ENION S.A. in Kraków as the Head of Transmission Services Management Office. Member of numerous working groups appointed by Polskie Towarzystwo Przesyłu i Rozdziału Energii Elektrycznej (Polish Society of Electrical Energy Transfer and Distribution).

Waldemar L. Szpyra Kraków / Poland He obtained the diploma of engineer electrician in the Faculty of Electrical Engineering of AGH University of Science and Technology in Kraków in 1975, and PhD – in the Faculty of Electrical Engineering, Automatics, IT and Electronics of AGH University of Science and Technology in Kraków in 1998. Now - an assistant professor in the Department of Electrical and Power Engineering of his University. He deal with modelling, state estimation and optimal control of power distribution networks using an artificial intelligence methods and electrical power management.

Power Losses as Necessary Own Needs of Network

POWER LOSSES AS NECESSARY OWN NEEDS OF NETWORK Jerzy Kulczycki / AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A. Waldemar Szpyra / AGH University of Science and Technology in Cracow

1. CAUSES OF LOSSES; ACTUAL, JUSTIFIED AND OPTIMAL LOSSES Output energy is smaller than input energy in each element of energy network. Network energy losses are the difference between the energy introduced into the network and the power received from the network. Network losses are most often classified by their sources of origin. Technical losses and commercial losses are distinguished. Technical losses of power are due to physical phenomena accompanying power flow in network or voltage in network. Based on these phenomena, the following classification is adopted: • current losses (load, lengthwise losses) dependent on load (Joule heat) • voltage losses (idle, crosswise losses) dependent on voltage (losses in dielectrics, losses of corona discharge, losses in transformer cores). Technical power losses are unavoidable in a network consisting of the elements in which those phenomena occur. Since each element of a network has resistance – flow of current produces heat, which is a loss of a part of the power transmitted. Live insulation also produces losses. Losses in resistance and in insulation of properly selected and used element of a network result from “the physics of the phenomena” taking place during power transmission. They do not occur due to wastefulness or mismanagement. It seems that own needs of network or, to be more precise, power own needs of network would be a more appropriate term to describe such losses. However, the term technical losses will be used in further parts of the text; as it is shorter, generally understood and generally used. Commercial losses are due to the fact that both input energy, and output energy are measured with certain errors. They are thus effects of energy trading issues. They are classified in the following way: • losses due to errors of measurement systems, mainly from high start up level of meters and accuracy class of the meters used - it can happen that losses due to errors of measurement systems are less than zero • losses resulting from registration system of energy sold, e.g. resulting from the system adopted for settlement, based on forecasts of energy consumption by small consumers. Losses in the case of different frequency of reading of various groups of meters and delays in meter readings constitute other examples of regulation losses. Regulation losses have positive and negative values, and in longer time periods their value is close to zero • unmeasured energy taken from network (illegal energy consumption).

Abstract Classification of network losses (balance difference) by sources of their origin was presented. It was demonstrated that balance difference is not sufficient to determine the technical losses in the network. Due to measurement errors and errors resulting from energy sold registration systems, balance difference often shows, in relation to actual losses, alternately inflated, underestimated or even negative values. Three methods of calculating actual losses based on reporting were presented. Impact of local energy sources, energy transits, distribution network operator decisions and contractual obligations with some consumers on losses factor were pointed out to.

balance losses (balance difference)

technical losses

commercial losses due to:

errors of measurement systems

voltage losses (no load losses)

current losses (load losses)

illegal power consumption

sale registration systems

Fig. 1. Classification of network losses by sources of their origin

Fig. 1. Classification of network losses by sources of their origin The notion of optimal losses will be explained on the example of power line. But let us define the notion of The notion of optimal losses will be explained on the example of power line. But annual cost first. Annual is a measure the expenditure let us cost define the notion of ofall annual cost first. connected with construction and operation of a network or an element ofAnnual a network, to oneofyear. cost referred is a measure all the expenditure connected with construction and Letoperation us consider a case of a planed power a specified load. Annual of a network or an element line of aofnetwork, referred to one cost year.of that line consists of fixed cost (cost of capital cost of operation) (cost of of power and energy Both components depend Let+us consider a caseand of avariable planed cost power line a specified load.losses). Annual cost of on line cross-section. Increase of cross-section causes increase of fixed cost and decrease of cost of losses, that that line consists of fixed cost (cost of capital + cost of operation) and variable cost is variable cost.ofThe dependence of annual costBoth and its components on cross-section is shown in Fig. 2. (cost power and energy losses). components depend on line cross-section. The cross-section at which the function of annual cost reaches minimum K , is Increase of cross-section causes increase of fixed cost and decrease ofrmincostan ofeconomic losses, cross-section of line sekthat . Energy losses variable with this cost. cross-section are optimal is floating The dependence of losses. annual cost and its components on cross-section is shown in Fig. 2. 30 000 The cross-section at which the function of annual cost reaches minimum Krmin, is Annual cost an economic cross-section of line sek. Power Energy losses with this cross-section are Annual fixed cost Annual variable cost optimal losses. Annual cost, [PLN]

periods their value is close to zero ■ unmeasured power energy taken from network (illegal power energy consumption). Balance network losses or, in short, balance difference or balance losses are the Jerzybetween Kulczycki; L. Szpyra/ AGH University of Science Technology in Cracow difference theWaldemar measured power energy introduced into a and network and the Michał Rudziński / ENION S.A. measured power energy received from the network. Balance difference is a sum of technical losses and commercial losses. classification ofin network losses by sources of origin is given in Fig. 1. BalanceThe network losses or, short, balance difference ortheir balance losses are the difference between the measured energy introduced into a network and the measured energy received from the network. Balance differLet us define other terms connected with technical losses: ence is a sum of technical commercial losses. ■ actual losses arelosses lossesand actually occurring in a given network, The classification of network losses by sources of origin network is given inwith Fig.optimal 1. ■ justified losses are losses that would occur their in a given power Let us define other terms connected with technical losses: distribution and proper operation of the network, • actual losses are losses actually occurring in a given network, ■ optimal losses are losses that occur in a network of a structure matching the load in • justified losses are losses that would occur in a given network with optimal power distribution and proper operation of the network, such a way that annual cost (or the sum of discounted costs during period) of that network reaches • optimal losses are losses that occurdepreciation in a network of a structure matching the load in suchthe a way that annual minimum. cost (or the sum of discounted costs during depreciation period) of that network reaches the minimum.

20 000

10 000

2 0 20

100

110

120

Line cross-section s, [mm ]

Fig. 2.2.Dependence of annual cost and components on line cross-section. Fig. Dependence of annual costitsand its components on line cross-section.

Annual costcost in sin environment is a is flata flat function, and and whenwhen the value of crossAnnual environment function, the value of cross-section differs from economic ek s ek section differs from economic cross-section, annual cost of the line changes relatively cross-section, annual cost of the line changes relatively slightly. slightly.In practice, the data for calculation of annual cost and economic cross-section are blurred. The precise valthe data for of annual economic cross-section ues In of practice, the components oncalculation which annual costs,cost e.g.and construction costs, load,are power costs are based are not known blurred. The precise values of the components on which annual costs, e.g. with spectra reflecting ranges of in advance, during line designing phase. The lines in Fig. 2 should be replaced construction costs, load, powerdata. costs As area result, based arethe notdiagram known ininadvance, during possible variability of those Fig. 2 will takeline the form as in Fig. 3. designing phase. The lines in Fig. 2 should be replaced with spectra reflecting ranges of possible variability of those data. As a result, the diagram in Fig. 2 will take the form as in Fig. 3.

slightly. In practice, the data for calculation of annual cost and economic cross-section are blurred. The precise values of the components on which annual costs, e.g. as Necessary Own Needs of Network construction costs, load, power costs are based are notPower knownLosses in advance, during line designing phase. The lines in Fig. 2 should be replaced with spectra reflecting ranges of possible variability of those data. As a result, the diagram in Fig. 2 will take the form as in Fig. 3.

Annual cost, [PLN]

30 000

Annual cost Annual fixed cost Annual variable cost

20 000

Fig. 3 shows that the values of economic cross-section, that is also of optimal losses, are “blurred” – they can be calculated with a certain error. The following conclusions can be drawn from the analysis of annual cost of the 0 20 70 80 of90line 100cross-section 110 120 30 components: 40 50 60 increase line and its increases fixed cost of the line Line cross-section s, [mm ] and decreases its floating cost. So, with the given projection of load, it is possible to reduceoflosses planned line, but itin the increases linecostconstruction expenditure. Fig. 3. Dependence annual costin andthe its components on line cross-section case of “blurred” data – broken line shows borders of Fig. 3. Dependence of annual cost and its components on line cross-section in the variabilityReduction of costs with the assumption thatbelow investmentoptimal expenditure and power losses bear an errorbut of ±5%. of losses losses is possible, it requires application of a case of “blurred” cost data – broken line shows borders of variability of costs with the assumption that investment expenditure power losses bear and an error of ±5%. bigger, more expensive cross-section consequently increases Fig. 3 shows that the values ofand economic cross-section, that is also of optimal losses, operating are “blurred”costs – they of can be calculated with a certain error. the network. The following conclusions can be drawn the analysis of annual cost of the line and its One should remember that from the data for calculating optimal losses arecomponents: not precise increase of line cross-section increases fixed cost of the line and decreases its floating cost. So, with the given (blurred). Sopossible the results calculating economic of the line and the projection of load, it is to reduceof losses in the planned line, but it cross-section increases line construction expenditure. 3 related cross-section of optimal can be guidelines in more activities aimed Reduction of losses below optimal losses is possible,losses but it requires application of a bigger, expensive cross- at section reduction and consequently increases of the network. of losses, butoperating should costs be treated as approximate, with some tolerance. One should remember that the data for calculating optimal losses are not precise (blurred). So the results The same conclusions can be justified with reference to other elements in the of calculating economic cross-section of the line and the related cross-section of optimal losses can be guidelines network transformers) and to abe network consisting ofwith those elements. in activities aimed (e.g. at reduction of losses, but should treated as approximate, some tolerance. The same conclusions can be justified with reference to other elements in the network (e.g. transformers) The following example illustrates the notions of actual, justified and optimal and to a network consisting of those elements. losses. 10 000

The following example illustrates the notions of actual, justified and optimal losses.

Example 1

Example 1 Two way fed line of equal load along its entire length and fixed cross-section s is Two way fed line of equal load along its entire length and fixed cross-section s is discconnected (cut) in disconnected (cut) one occur power nodes (Fig. 4). Actual losses occur in this working one power nodes (Fig. 4). Actualinlosses in this working status

status.

Pr P0,5

Legend: l – length of network line lr – distance between cut point and feeding point Pr – power losses when the line is cut in point r P0,5 – power losses when the line is cut in half length

4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.00

0.25

0.50

0.75

1.00

lr l

Fig.line4.of equal Network line ofofpower equal load dependence Fig. 4. Network load – dependence losses on network–discconnected (cut) placeof [3] power

losses on network

disconnection (cut) place [3] In a two way fed line of equal load along its entire length, but cut, actual losses

Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A.

In a two way fed line of equal load along its entire length, but cut, actual losses depend on location of cut point. The dependence is shown in Fig. 4. If there were no contraindications for change of cut point (e.g. resulting from the requirement of certainty of supply), the line should be cut in half-length. Then the smallest losses would occur. They would be justified losses. Let us assume that the network is cut at the beginning of the line – with consumption of increased requirements of certainty of supply, equipped with automatic stand-by switching-on. In such a case, actual losses will be four times bigger than when the line is cut in half-length, but they will be justified losses. If at the design stage the cross-section of the line sek was selected in such a way that the annual costs (not losses!) were the smallest, then the losses that would occur with such a cross-section and line cut in its half-length would be optimal losses. Depending on whether the existing cross-section of the line s is bigger or smaller than economic cross-section sek, the comparison of justified losses and optimal losses would be the following: • if s > sek, then optimal losses would be smaller than justified losses • if s < sek, then optimal losses would be bigger than justified losses.

Sum up It follows from the above considerations that: • Balance losses (balance difference) do not constitute sufficient information for determining technical losses occurring in a network. • The volume of justified losses in a single element of a network can depend on various circumstances. • Actual losses are bigger or equal to justified losses, and optimal losses can be bigger, equal or smaller than actual and/or justified losses. • Minimisation of losses (costs of losses) cannot be the most important objective for a network operator. Power supply of specified quality characteristics and at the lowest cost is the fundamental objective of network operation. Costs of losses are one of the many components of network operation costs. 2. LOSSES FACTORS Network efficiency and relative percentage losses can be calculated based on absolute, that is calculated e.g. in MWh, volume of balance losses. Relative percentage losses factor, and consequently, network efficiency are defined in different ways. That is why one should give three of such definitions. The differences of the values of losses factors can result, inter alia, from different ways of taking into consideration of energy distributed from the network of a given distribution company (DC) to the networks of neighbouring distribution companies. The ways of calculating balance losses ratio according to G-10.7 Report will be presented below.

Fig. 5. Energy balance of distribution company

Let us adopt the following symbols: Ewp – total input energy into distribution network (DN); Eod – total output energy from DN; ENN/110 – input energy into DN through LV/110 kV transformers; E110/NN – output energy from DN through UHV/110 kV transformers; Eg – input energy into DN from energy plant connected to DN; EpDC – energy taken from neighbouring DC; EoDC – energy given to neighbouring DC; Es – energy supplied to final consumers, including the one consumed illegally; Epw – own needs (energy for DC own needs); Epwe – energy used for water pumping in water power plants; ∆E – power losses in the network.

Power Losses as Necessary Own Needs of Network

The following relations occur: • input power into network (1)

• output power from network (2)

• balance losses (balance difference, absolute value)

(3)

Since May 1995, percentage balance losses factor (balance difference) in G-10.7 Report is defined in the following way: (4)

In power industry reporting (G.10.7 Reports) valid till April 1995, balance losses factor (balance difference) were calculated in a different way, that is: (5)

It is obvious that using different definition formulas one can obtain different results. Also rating of distribution companies classified by losses factor calculated according to different formulas can be different. It will be illustrated on an example given further in the article. The share of some components of input power into network Ewp and output power from network Eod affect the value of balance losses factor (balance difference). It refers to input power Eg to network DC from power plants connected to distribution network DC in total input power into network Ewp and to the share of output power EoSD given to neighbouring network DC. Table 1. Example of relation of balance losses factor on production of local power plant Subsequent year

Eg – energy production of local power plant [GWh]

Es – sale of energy to end consumers [GWh]

890

4336

∆E% – balance losses factor (balance difference) [%] 13,96

752

4559

14,99

0,16

1026

4805

13,68

0,21

1014

4682

13,04

0,22

1544

4642

12,00

0,33

Eg/Es 0,21

As for the power plants connected to distribution network, the shorter term – “local power plants” will be used. The influence of local power plants on the volume of energy losses depends on the volume of the energy they put into network and on location of the power plant in relation to other sources feeding this network, e.g. on UHV/110 or 110/MV station. When the power of the energy plant is relatively small and meets the demand of a close fragment of the network, the energy from local power plants usually has a shorter distance to consumers than the energy coming from LV station – so it is distributed from the network with smaller losses. The data of one of the distribution companies, presented in Table 1, illustrate that situation.

Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A.

And when a local power plant also covers the load of distant consumers, e.g. surplus of input power into network at a given voltage is transformed into higher voltage – the work of the local power plant can increase power losses. If a local power plant puts power into 110 kV network of the power of hundreds MW distributed in a few 110 kV networks, power losses in some distribution networks will decrease, and in some – they will increase; but: • the biggest growth of losses occurs in a network of that distribution network to which the local power plant is connected • losses in all distribution networks calculated together can increase or decrease Tables 2 and 3 refer to such a situation. Table 2. An example of dependencies of balance losses factor in four distribution networks and in a 110 kV network of national power system (KSE) on the work of local power plant (heat and power generating plant) of 500 MW, connected to network DC-1 Power losses in MW in a 110 kV network of four distribution networks and a network of national power system (KSE), planned winter peak demand - 2015

Variant

DC-1

DC-2

DC-3

DC-4

KSE network

Initial

17,8

13,3

11,5

27,9

After launching of heat and power generating plant of the power of 500 MW Effect of launching heat and power generating plant

31,1

12,5

10,5

22,5

+13,3

–0,8

–1,0

–5,4

+6,3

Table 3. An example of dependencies of balance losses factor in five distribution networks and in a KSE 110 kV network on work of two heat and power generating plants of combined power of 330 MW, connected to distribution network DC-2 Power losses in MW in a 110 kV network of five distribution networks and the network of national power system (KSE), planned winter peak demand - 2015

Variant Initial After launching heat and power power ofgenerating plant generating plant of the power of 500 MW Effect of launching heat and power generating plant

SD-1

SD-2

SD-3

SD-4

SD-5

17,8

13,3

11,5

27,9

10,8

16,1

14,9

10,6

26,4

11,9

-1,7

+1,6

–0,9

–1,5

+1,1

KSE network

–1,4

Most of power transit to neighbouring distribution networks is in 110 kV, which is connected smaller percentage losses power Most of power with transitconsiderably to neighbouring distribution networks is in than 110 kV, whichdistribution is connectedto with considerably end smaller percentage lossesvoltage than power distribution to endofusers, fedtransit at lower(giving voltagepower levels. do In the case of users, fed at lower levels. In the case power powerneighbouring transit (giving power do neighbouring distribution networks), lossesand are smaller and network distribution networks), percentage lossespercentage are smaller network efficiency - bigger. The following calculation example explains it: efficiency - bigger. The following calculation example explains it: Example 2Example 2 ENN/110

ENN/110 150

110

DC B area EoSD 39.2

DC A area ΔE

ΔE

10.8

100

Fig. 6. Energy balance of distribution companies – influence of calculation methodology on the volume of balance losses factor (balance difference)

Fig. 6. Power Energy balance of distribution companies – influence of calculation

Balance losses on factors (balanceofdifference) for distribution companies with energy balance as in Fig. 6 methodology the volume balance losses factor (balance difference) [formula (4)] are as follows: • distribution company A

Balance losses factors (balance difference) for distribution companies with power energy balance as in Fig. 6 [formula (4)] are as follows: ■ distribution company A E%

Ewp E

Eod

100%

110 100 100% 9.09% 110

Power Losses as Necessary Own Needs of Network

• distribution company B

■ distribution company B And the factors calculated by the use of the method valid to April 1995 [formula (5)] are as follows: 150 139.2 E% 100% 9.75% • distribution company 100 10.8 A

In the case of distribution company transmitting power energy to the network of a neighbouring company, the result of the calculations depends on the method. It is worth noting that if there were two distribution company ratings by balance losses • distribution companydifference) B factors (balance calculated by the use of the two methods, then the mutual relation of companies A and B in the two ratings would be different. In the rating developed according to the now valid methodology of calculation, company B would have a smaller losses factor (7.20%) than the factor of company A the rating developed according energy to oldertomethodology would be justcompany, the In(9.09%). the case In of distribution company transmitting the network ofita neighbouring result ofthe theopposite; calculations depends on the method. It is worth noting that if there were two (9.09%) distribution company distribution company A would have a smaller losses factor ratings by balance losses factors (balance difference) calculated by the use of the two methods, then the mutual factor of company B (9.75%). Thebedifferences efficiency relationthan of companies A and B in the two ratings would different. In of the network rating developed according to the calculated for Poland by thecompany use of Bthose 2.5÷3.0%, and for now valid methodology of calculation, wouldtwo havemethods a smallerare losses factor (7.20%) than the factor of company A (9.09%). In the rating developed according to older methodology it would be just the opposite; individual distribution companies they can be even bigger. distribution company A would have a smaller losses factor (9.09%) than factor of company B (9.75%). The differences of network efficiency calculated for Poland by the use of those two methods are 2.5÷3.0%, and for 3 companies they can be even bigger. individualExample distribution

This example will show the influence of power transit (distribution of power Example energy3 to neighbouring distribution networks) on losses factor (balance difference). This influence ofcompanies power transit energytotoone neighbouring Let usexample assume will thatshow threethe distribution do(distribution not transmitofpower another, distribution networks) on losses factor (balance difference). Let us assume that three distribution companies do not transand that their balances are as presented in Fig. 7. mit power to one another, and that their balances are as presented in Fig. 7.

9.5

ENN/110

100

DC A area

DC B area

DC C area

ΔE ES 90.5

ΔE

ES 90

ΔE

10.5

ES 89.5

Fig. 7. Energy balances of three distribution companies – variant without power transits between the networks of the companies

Fig. 7. Power Energy balances of three distribution companies – variant without Balance lossesbetween factors (balance difference) according to formula (4) are: power transits the networks of thecalculated companies • distribution company A Balance losses factors (balance difference) calculated according to formula (4) are: ■ distribution company A • distribution company B

■ distribution company C Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow

100 .5 Michał89Rudziński 100% / ENION 10.50% S.A. 100

• distribution company C The order of distribution companies set according to that factor is as follows: 1) distribution company A – 9.50% 2) distribution company B – 10.00% 3) distribution company C – 10.50%. The order of distribution companies set according to that factor is as follows: 1) distribution company A – 9.50% 2) distribution company B – 10.00% Let us see how the 3) distribution company C – exchange 10.50% of 20 power energy units without change of losses distribution company C isofmade, presented in between distribution companyofB20and Let us see how the exchange energy units without change losses as between distribution company 8. B andFig. distribution company C is made, as presented in Fig. 8. ENN/110

ENN/110

100

DC A area

DC B area

ΔE

9.5

ES 90.5

ΔE

DC C area

ΔE

ES 90

10,5

ES 89.5

Rys. 8. Energy balances of three distribution companies – variant of exchange of 20 energy units between distribution company B and distribution company C

Fig. 8. Power Energy balances of three distribution companies – variant of exchange of 20 power energy unitsdifference) between distribution company B Aand Balance losses factors (balance of distribution company willdistribution not change, company but the factors for distriC company B and distribution company C will be: bution • distribution company B Balance losses factors (balance difference) of distribution company A will not change, but the factors for distribution company B and distribution company C will be: distributioncompany company • ■distribution CB

The order of distribution companies by balance losses factor (balance difference) will be as follows: 1) DC B – 8,33% 11 2) DC C – 8,75% 3) DC A – 9,50%. It is mainly 110 kV network that participates in transferring energy to neighbouring companies. The losses connected with energy transfer at this voltage are considerably lower than the losses accompanying energy flow to consumers of lower voltage demand. If in a given distribution network the energy is transferred to a neighbouring distribution network, then in the network of the given company the volume of energy introduced into Ewp and given to Eod must grow. In the case of calculating balance losses factor (balance difference) from formula (4) the considerable growth of transit and thus the growth of the denominator (e.g. by a few tens of hundreds) is accompanied by increase of losses, that is numerator (e.g. by a few tens of percent). So energy transit to neighbouring companies decreases balance losses factors (balance difference). The calculations of example 3 point out to that. The diagrams shown in Fig. 9 present an example of the dependencies of balance losses factor ∆E% on the energy given to neighbouring distribution companies EoSD and the dependence of the relation on balance losses factor to balance losses factor without export of energy to the volume of energy given to neighbouring distribution networks. The diagrams were developed with the assumptions that the total energy goes to the analysed distribution network from UHV network, the energy supplied to end users Es = 5 000 GWh, energy losses in the network without transit are 10%, ∆E = 500 GWh, energy losses induced by power transit to 110 kV neighbouring distribution network are 2.5% of the given energy.

Own 0.8Needs of Network

0.6 1.2

4 Balance losses factors Relation of balance losses factor to losses factor without power export power

0 6

1.0

1.0 0.8

Relation of balance losses factor to losses factor without energy export, [

Balance losses factors, [%]

Relation of balance losses factor to losses factor without power export powerPower Losses as Necessary

0.4 Relation of balance losses factor to losses factor without energy export, [%]

Balance losses factors, [%]

Balance losses factors 10

0.2

1 000 2 000 3 000 4 000 5 000 6 000 7 000 0.6 8 000 9 000 10 000

Energy exported to neighbouring distribution companies, [GWh] 4

0.4

2 0.2 Fig. 9. Dependence of balance losses factor (balance difference) ΔE% on power energy given to neighbouring distribution company EoSD and dependence of relation 0 0 of0 balance losses to6 balance 1 000 2 000 3 000 4factor 000 5 000 000 7 000 8losses 000 9 000factor 10 000 without power energy export on Energy neighbouring distribution companies, [GWh] volume of exported power toenergy given to neighbouring SDDC

Fig. 9. Dependence of balance losses factor (balance difference) ∆E% on energy given to neighbouring distribution company EoSD and dependence of

Influence ofto network companies on% losses factor Fig. 9. ofDependence balance losses factor difference) ΔE on power relation balance lossesof factor balance losses factor (balance withoutconsolidation energy export on volume of energy given to neighbouring DC energy given to neighbouring distribution company EoSD and dependence of relation ofInfluence balance losses factor 4to companies balance lossesconsolidation factor without power energy export on ofExample network on losses factor volume of power energy given to neighbouring SDDC

Let us assume that distribution companies B and C, with power energy balance as Example 4 inus example 3, (fig. 8), would merge into oneC,factor company. Power Energy Influence of network companies consolidation onBlosses Let assume that distribution companies and with energy balance as inbalance exampleafter 3, (fig. 8), would consolidation willEnergy be as in Fig. 10. merge into one company. balance after consolidation will be as in Fig. 10..

Example 4 Let us assume that distribution companies B and C, with power energy balance as ENN/110 in example 3, (fig. 8), would merge into one company. Power Energy balance after 200 consolidation will be as in Fig. 10. DC B+C area

ENN/110 200

ΔE

20.5 DC B+C area ΔE

20.5

ES 179.5

Fig. 10. Energy balance of consolidated distribution companies 179.5

Fig. 10. Power Energy balance of consolidated distribution companies

Balance losses factors of those companies before merger would be for distribution network of DC B – 8.33%, for distribution network of DC C – 8.75%. Balance losses factor after consolidation will be: Fig. 10. Power Energy balance of consolidated distribution companies

In this case change of properties, without any technical changes, including no changes in energy distribution, will cause a significant growth of losses factor. It can happen in the case of consolidations of distribution 13 networks between which there are significant energy transits. 13

Sum up The following conclusions can be drawn from the analysis of formulas (4) and (5): 1. The methodology of calculating losses factor (balance difference) considerably affects its value 2. Exchange of energy between neighbouring distribution networks (mutual provision of transit services) decreases balance losses factors (balance difference) even if it leads to growth of absolute losses 3. Merged (consolidated) distribution networks can have a percentage balance losses factor higher than loss factors of individual companies before merger (with unchanged values of absolute losses, calculated e.g. in MWh).

Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A.

3. COMMERCIAL LOSSES As mentioned in chapter 1, commercial losses are caused by errors of measurement systems, errors resulting from sale registration systems and illegal energy consumption. Errors of measurement systems Example 5 Let us consider the case of a network element, e.g. line with energy measurements at the beginning and at the end. Let us assume that in a certain time period between meters readings, the energy actually transmitted from the line is 100 kWh; actual energy losses in the line are 0.5 kWh; both meters, at the beginning and the end of the line, are 0.5 class; the meter at the beginning of the line has negative deviation: its indications are by 0.4% lower than the actual energy flow; the meter at the end of the line has a positive deviation: its indications are by 0.3% higher than actual energy volume. The assumptions indicate the following : • actual energy going to the line is 100.5 kWh • target energy as going to the line is 100.5 – 0.402 ≈ 100.1 kWh • target energy as received from the line is 100 + 0.3 = 100.3 kWh • the difference between the target energy at the beginning and at the end of the line, that is the losses are: 100.1 – 100.3 = –0.2 kWh. The same example indicates that the balance losses (balance difference) can significantly depend on errors of measurement systems. The error of balance difference is the bigger the smaller the actual losses of the network are. In practice, the losses analysis refers to network fragments of much bigger losses, from few to over ten percent. But in extreme cases, balance losses (balance difference) can be lower than zero due to errors of measurement systems. Energy sold registration systems Bigger and more frequent errors can be caused by systems of registration of energy sold. The reports showing energy sold in reports in individual months can have errors. It refers in particular to the energy sold from LV network. The errors can be due to adoption of e.g. the following rules in meter readings: 1. Meters of energy transmitted to a network are read every month 2. Consumers are divided into two groups, e.g. A and B 3. In the first group of consumers meters are read in odd months, that is in January, March, May..., and in the second group - meters are read in even months – that is in February, April, June... 4. The meters readings in each group take one month. Energy consumption in a month is assigned to the 15th day of the given month and is shown as energy consumption in both groups in a given month. So, e.g. energy consumption by consumers of group A, read in the period of in 1st to 31st of January, is assigned to 15th of January and is indicated in reports as energy consumption by group A and B consumers in January. Considerable differences between the quantity of energy shown in reports as delivered to consumers and the quantity of energy actually delivered to consumers in individual months can be an effect of “shift of energy consumption readings collection”. As a consequence, the specified balance losses (balance difference) are affected by the adopted system of settlement, based on energy consumption forecasts by small retail consumers. In relation to actual losses, the values of balance losses (balance difference) are alternately inflated and understated (“waving of losses”). Example 6 Let us consider a simple case in which: • energy transmitted to the network is read once a month • consumers are divided into two groups A and B, with meter readings every two months. Meters are read in odd months for group A consumers, and in even months for group B consumers • power consumption by the two groups differs considerably, which can be an effect of random division of the consumers into those two groups. Let us assume that energy demand and input energy into the network in individual months by all consum-

Power Losses as Necessary Own Needs of Network

ers are constant and are 100 MWh and 110 MWh, respectively; actual losses in individual months are thus also constant and are: 110 – 100 = 10 MWh. Energy consumption measured in two month periods is: for consumers of group A – 105 MWh, and for consumers of group B – 95 MWh. Balance losses (balance difference), calculated as a difference of input energy into the network and energy sold, will thus in odd months be 110 – 105 = 5 MWh, and in even months - 110 – 95 = 15 MWh. Such a variability of losses will hinder or make their fair analysis impossible. The errors concerning the quantity of energy delivered to consumers, shown in reports, can be caused by the system of settlement based on energy consumption forecast for small consumers. Some consumer service systems take into consideration variability of monthly energy demand during the year. Calculation of forecasted energy consumption for each consumer can be based, for example, on average daily consumption identified for this consumer last year, in the same months for which the consumption forecast for the next year is calculated. Such a forecast can also be wrong if, for example, a forecast for the coming severe winter, is made based on consumption during last, mild winter. The smaller the network for which losses balance is made, the bigger possibility of such things happening. Balance losses (balance difference) can be negative. It hinders identification of the causes of losses and chances of preventing them. It means that there is a need to develop calculation methods that would give a realistic picture of energy consumption calculated based on reporting and actual data. Figure 11 presents monthly balance difference in one of the distribution companies in 1993–2007 in 110 kV network, jointly in MV and LV networks, as well as the total balance difference in the entire distribution network. The diagram shows the cycle character of balance difference, resulting from seasons of the year, and distortion of balance difference in a MV and LV network, caused by big influence of registration losses. An analysis of balance should be made in combination with An an analysis of network inputdifference and output energy, and causeddifference by big influence of registration losses. analysis of balance sales. should be made in combination with an analysis of network input and output

powerenergy, and sales.

150 100 50 0 Losses and balance difference in a 110 kV network Losses and balance difference in MV and LV network

-50

Total losses and balance difference

Fig. 11. Balance of distribution 1993–2007 Fig. 11. difference Balancein one difference in networks one of indistribution

January 07

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networks in 1993–2007

Fig. 12 was developed based on the data from Fig. 11 and presents diagrams made in draw system, i.e. Fig. 12 was developed based on the data from Fig. 11 and presents diagrams each point in the diagram is a sum of energy from the previous 12 months, which is, respectively, balance difmade drawnetwork system,input i.e. each pointenergy in theordiagram is notion a sum ofofdraw power energywill from ference or in energy or output sales. The diagrams be discussed in thebelow. previous 12 months, which is, respectively, balance difference or power energy detail

network input or output power energy or sales. The notion of draw diagrams will be discussed in detail below.

Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A.

Losses and balance difference in 110 kV network Losses and balance difference in MV and LV network

1 000

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800 600 400

200

Fig. 12.Fig. Losses andLosses draw balance 12 monthsdifference in 1994–2007 12. anddifference draw inbalance

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Losses and balance difference drawn, [GWh]

1 200

in 12 months in 1994–2007

4. METHODS OF CALCULATING POWERconsumption CONSUMPTION BASED ON REPORTING Methods of calculatingACTUAL actual power based on reporting data DATA Below please find a presentation of three ways of calculating actual energy consumption based on reBelow please find presentation of three byways of calculating power porting. The concepts of the firstatwo ways were presented J. Sumera (ZE Tarnów actual SA). They were further energy consumption of the firstcompany. two ways were developed in publications [1] based and [6].on Thereporting. third way isThe usedconcepts in one of distribution

presented by J. Sumera (ZE Tarnów SA). They were further developed in

Idealisation method publications [1] and [6]. The third way is used in one of distribution The method is based on the observation that maximum energy consumption occurs in winter months, networkscompany. minimum – in summer months, and consumption in individual months can be presented as a diagram similar to cosine curve. Changing daylight period and changing temperature during the year are the basic causes of such Idealisation method a variability of energy consumption. Based on that it is assumed that energy consumption in individual months of the yearThe is a cosine curve and the course Energythat consumption in individual method is – based on theis idealised. observation maximum power months, energy given in reporting, was approximated with minimum the method of [6]. The consumption occurs with in cosine winterfunction months, – the in smallest summersquares months, andfollowing formula for idealised energy consumption Eid in individual months of the year was obtained after reduction consumption in individual months can be presented as a diagram similar to cosine verified by calculations:

curve. Changing daylight period and changing temperature during the year are the basic causes of such a variability of power energy consumption. Based on that it is (6) assumed that power energy consumption in individual months of the year is a cosine curve – and the course is idealised. Power Energy consumption in individual months, given in reporting, was approximated with cosine function with the method of the where: Eid – energy consumption after idealisation, Eav – average value from 12 months of energy consmallest [6]. The following formula forenergy idealised power energy consumption value of consumption in months: January, February, sumption in thesquares year considered, Emax – average E in individual months of the year was obtained after reduction verified by November and December of the year considered. id calculations: The method of cleaning statistical data Fig. 13 presents the relation between energy consumed in settlement period and energy consumption 1 EidtheEassumptions Emax cosx (6) read in the month. The relation is true with that: av 6 • there are two groups of consumers for whom the period between meter reading (settlement period) is 2 months, and meter readings for the consumers of a given group take a month (reading period) • readings of one group in a given month are added up as consumption of both groups of consumers and assigned to 15th day of readings month. So the energy read during the whole month is treated as energy read on 15th day of the given month.

Power Losses as Necessary Own Needs of Network

Fig. 13. Energy consumed and read (sold) in settlement period [1]

Fig. 13 shows that energy sold is not the energy actually consumed by the two groups of consumers in readings month, but the energy consumed by one of the groups in settlement period (of two months). Calculating the actual energy consumption was given a working name of “cleaning” the statistics of energy consumption. [1] and [6] show the formula derived with the assumptions given above:

(7)

(n ) where: Eocz – energy consumption in n-th month after cleaning statistical data, Es( n ) ; Es( n −1) ; Es( n − 2 ) – energy sold in n-th, n-1, and n-2 months.

The method of draw diagrams It is based on an observation that registration losses “wave” and in longer time periods their value is close to zero. Balance difference is analysed based on aggregated monthly data. Multiple number of the previous 12 months is always the summation period. Multiple number of 12 months is adopted on purpose, due to the fact that it covers a full annual weather cycle, eliminates registration losses and reduces the impact of imperfections of the settlement system for consumers of energy of low voltage. Fig. 12 is an example of draw diagrams. Application of cleaning and idealisation methods - example Fig. 14 presents energy consumption data according to reports and energy consumption calculated by the use of cleaning method. The figure refers to the fragment of the network of monthly consumer energy supply of 22÷37 GWh and provides quantities of energy sold and “cleaned” in two year period. 40 35

Energy, [GWh]

30 25 20 Energy consumed according to reporting

Energy consumed “cleaned”

10 5

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Fig. Fig. 14. Actual energy energy consumed, calculated by the use of by cleaning method and read from consumer energyfrom supply reporting [1] 14. Actual consumed, calculated the use of cleaning method and read consumer energy supply reporting [1] g

Str. 74 w. 6 jest:

Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A.

And Fig. 15 presents quantities of energy “cleaned” and “idealised”, supplied to consumers in one year in a network of monthly sale of 6÷12GWh. 14

Energy sold

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Energy, [GWh]

10 8 6 4

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Monthmethod and idealisation method and by readings (according to sales reporting); Fig. 15. Actual energy consumed, calculated by the use of cleaning network of consumer energy supply of 6 ¸ 12 GWh/month. [6]

Fig. 15. Actual power energy consumed, calculated by the use of cleaning method Based on reporting onmethod energy supplied consumers, the presented methods enable calculation of the and idealisation and bytoreadings (according to sales reporting); network of quantityconsumer of energy power actually energy suppliedsupply to consumers, of excessive of 6 elimination 12 GWh/month. [6] inflating and underestimating of

losses in subsequent months, the so called losses waving. Fig. 16 presents results of calculating energy losses during the year in one of the power plants. Individual Based on ofreporting on power curves represent results the calculations made: energy supplied to consumers, the presented a) based on input energy balance and energy from the network methods enable calculation of thesoldquantity of power energy actually supplied to b) by the use of J. Horak [2] method, based on energy sold from the network consumers, elimination of excessive inflating and underestimating of losses in c) based on input and output energy balance, where output energy was calculated from energy sold, by the subsequent months, use of idealisation methodthe so called losses waving. presents results ofoncalculating power losseswas during the year one d) by the Fig. use of16 J. Horak method, based output energy, whereenergy output energy calculated fromin energy sold, by the use of idealisation method. of the power plants. Individual curves represent results of the calculations made:

20 15 10 5

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0 January

Energy losses (balance difference), [MWh]

a) based on input power energy balance and power sold from the network 50 use of J. Horak [2] method, based on power energy sold from the network b) by the a) 45 c) based on input and output power energy balance, where output power energy was b) 40 c) calculated from power energy sold, by the use of idealisation method d) 35 d) by the use of J. Horak method, based on output powerenergy, where output power 30 energy was calculated from power energy sold, by the use of idealisation method. 25

Month

Fig. 16.losses Monthly power energy losses Fig. 16. Monthly energy in DC network (legend in the text)

in DC networkZE (legend in the text)

Power Losses as Necessary Own Needs of Network

Sum up Errors of measurement systems, errors resulting from registration systems of energy sold and illegal energy consumption are causes of commercial losses. The value of balance losses (balance difference) is seen in relation to actual losses, and often the values are inflated or underestimated (“losses waving”). It is caused by commercial losses, and in particular by errors resulting from registration systems of energy sold. In extreme cases, balance difference can be negative. Three methods of calculating actual energy consumption and actual losses based on reporting data were presented: • idealisation method • method of cleaning statistical data • method of draw diagrams. Based on reporting of consumer energy supplied, the methods enable calculating the energy actually supplied to consumers and eliminating the effect of “losses waving”. The following conclusions can be drawn from the applications of the methods presented: 1. There can be significant differences between energy supplied to consumers and energy indicated in reports, and the quantity of energy calculated by the use of these methods 2. The method of draw diagrams and idealisation method are less work consuming than cleaning methods and enable the following calculations: • method of draw diagrams – annual actual losses • idealisation method – course of actual consumption 3. The cleaning method requires (in comparison with the two other methods) longer calculations based on knowledge of the causes of distortions in meter readings 4. The method of draw diagrams does not have any assumptions concerning the course of energy consumption. Idealisation method assumes cosine curve course of monthly energy quantities, and cleaning method assumes that daily energy consumption in a given month is the same. It follows from the analysis of these assumptions that the cleaning method is the most accurate one 5. Comparison of the courses of energy consumption according to reporting and “cleaned” energy indicates that the cleaning method shifts actual energy consumption towards previous months. Technical losses independent of distribution network operator Decisions of ultra high voltage (UHV) network operator (Area Dispatch Centres) can affect losses in the fed 110 kV distribution network. The volume of these losses is affected in particular by: 1. Power distribution in a UHV network 2. Voltage regulation in UHV/110 kV stations 3. Decisions on 110 kV network structure. The network is owned by operators of distribution networks, but the lines that significantly affect power transmitted from power plant or serving to transmit power between companies are coordinated by Area Dispatch Centres 4. Construction of new UHV/110 kV stations. Also contractual obligations resulting from contracts with customers can affect increase of losses in MV networks. It refers to cut locations in MV networks. Load flow in a UHV network Changes in power generation among power plants affect on load flow in UHV network, and consequently, the load of individual UHV/110 kV stations. Change of these loads leads to change of load flow and power losses in 110 kV network, which is illustrated in figure 17. 110 kV network of a distribution company is fed from two stations of the highest voltage: 220/110 kV station and 400/110 kV station. The figure shows (in relative units) active power flow in UHV lines feeding the stations (the total power coming to 110 kV network via the two stations feeding the network is a reference unit). In normal working conditions, both stations are loaded with active power of 0.5. If there is a change of power generated in power centres feeding UHV network, power flow in this network (values in brackets) will also change considerably. The changes will cause changes of load of LV/110 kV stations (up to 0.2 and 0.8 of reference power, respectively). These changes will result in changes of power flow and losses in the 110 kV network.

Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A.

Fig. 17. Power flow in a fragment of 400/220/110 kV network

Voltage regulation in UHV/110 kV stations Transformers and autotransformers in stations of the highest voltage are equipped with facilities for longwise voltage regulation. The voltage of 110 kV is regulated. This regulation is handled by the operator of the UHV network (Area Dispatch Centres). Voltage levels of 110 kV in UHV stations affect power flow in 110 kV network fed from those stations. Equalising current flows is due to the difference of voltages feeding 110 kV network. Since in 110 kV network reactance is much bigger than resistance, X >> R, equalising flow of reactive power is much bigger than the flow of active power. Let us consider line A – B, connecting stations A and B, belonging to different network companies. In 110 kV A – B line, flow of reactive power Q through line of the resistance R will cause losses of active power: (8) In this case, transit of power and reactive power from station A to station B belonging to another company will cause active losses of power and energy in distribution network A. Currently (July 2009) this transit is free of charge.

Configuration of 110 kV network structure The structure of connections of 110 kV network obviously affects power flow and losses in that network. Apart from the function of a distribution network, 110 kV network that is owned by distribution companies also plays the role of transmission network. That is why it is Area Dispatch Centres that decide, to a great extent, about the structure of connections of that network. Construction of new UHV/110 kV stations Construction of new UHV/110 kV stations and new lines transmitting power from those stations to 110 kV networks shortens the power transmission distance via 110 kV network and decreases power flows in individual 110 kV lines; as a result of that, losses in 110 kV networks decrease. Location of disconnetion points in MV networks MV networks are built as closed networks but work as open ones; and location of disconnection points (cuts points) of those networks affect the volume of power losses. So selection of cuts points location is a subject for optimisation. The cut points should be the ones at which all the technical conditions (e.g. concerning voltage drops, cable and wire load capacity) are met, and power losses are the smallest. There are cases in which cuts location selection is a result of meeting the requirements of certainty of supply to some consumers, and not of minimisation of losses.

Power Losses as Necessary Own Needs of Network

Sum up Decisions of UHV network operator and contractual obligations resulting from contracts with some customers can affect the losses of the fed 110 kV distribution network. The volume of these losses is affected in particular by: • power flow in UHV network • voltage regulation voltage in UHV/110 kV stations • decisions on 110 kV network structure • construction of new UHV/110 kV stations. Changes in distribution of power generation among power plants affect power flow in the UHV network, and consequently, the load of individual UHV/110 kV stations. Change of these loads leads to change of power flow and power losses in 110 kV network. This regulation is handled by the operator of the network of the highest voltage. Voltage levels of 110 kV in UHV stations affect power flow in 110 kV network fed from those stations. Equalising current flows is due to the difference of voltages feeding 110 kV network, and, as a consequence, energy losses. The structure of connections of 110 kV network obviously affects power flow and losses in that network. 110 kV network is owned by distribution companies, and the lines that significantly affect power output from the power plant or that are used for power transit between distribution networks are coordinated by Area Dispatch Centres. By shortening the distance of power transmission via 110 kV network and decreasing power flow in 110 kV lines, construction of new UHV/110 kV stations decreases losses in 110 kV networks. Taking into consideration the requirements of increased certainty of supply for some consumers can be connected with increase of power losses in networks supplying those consumers. 5. OTHER FACTORS OF NETWORK OPERATION QUALITY Classification of losses in network and various losses factors used to assess network efficiency were presented in previous chapters. Losses factors cannot, however, be the only basis for assessing a network both for its structure and operation. In market economy, company operation is assessed based on financial indicators, such as liquidity, active participation, profitability and debt ratio. In electric power distribution companies efficiency measure could be composed of unit costs of power distribution, measured as a quotient of total costs of operation connected with power transmission and distribution and the total quantity of power that was transmitted through the network of the company (supplied to end consumers or neighbouring companies) in a given time period (e.g. in a year). Unit costs of power transmission (distribution) in networks of individual organisational units of the company or at individual voltage levels, or, finally, in individual facilities can also be determined. One should remember, however, that distribution companies operate in the areas that differ in population density, industrialisation level and land features. These factors significantly affect on a network structure and extent of its use. That is why unit costs of power distribution (and power losses, for that matter) are different in the companies operating in different areas. Reduction of distribution unit costs is possible by reducing costs and/or increase of the quantity of the power supplied to consumers. Both options are limited, however. Operation of distribution companies is regulated by the Act Energy Law [7] and regulations to that Act, and in particular “tariff” [4] and “system” [5] ordinances. Meeting the requirements of that legislation often leads to investments, and, consequently, to growth of costs. Reduction of power losses in electric power networks operated by those companies is one of the ways to reduce costs. Losses can be reduced by various operational activities or by investments. Operational ways of losses reduction in distribution networks include, inter alia, voltage regulation in those networks, reducing voltage and current asymmetry and distortion, change of cut points of medium voltage network. It should also be noted that e.g. in some extreme cases voltage regulation that reduces power and energy losses can reduce the power consumed by consumers, and thus reduce income on transmission charges.

Jerzy Kulczycki; Waldemar L. Szpyra/ AGH University of Science and Technology in Cracow Michał Rudziński / ENION S.A.

LITERATURE [1] Bogacz S., Więcek M., Estymacja strat energii w wybranym zakładzie energetycznym, diploma thesis. Wydział Elektrotechniki, Automatyki i Elektroniki AGH, Kraków 1996. [2] Horak J., Gawlak A., Szkutnik J., Sieć elektroenergetyczna jako zbiór elementów. Wydawnictwo Politechniki Częstochowskiej, Częstochowa 1998. [3] Horak J., Popczyk J., Eksploatacja elektroenergetycznych sieci rozdzielczych. WNT Warszawa 1985. [4] Ordinance of Minister of Economy of 2 July 2007 on detailed principles of development and calculation of tariffs and settlements in electric power trading (Journal of Laws of 18 July 2007, No 128, pos. 895). [5] Ordinance of Minister of Economy of 4 May 2007 on detailed conditions of electric power system functioning (Journal of Laws No 93 of 29 May 2007, pos.623). [6] Rutowicz R., Szacunek strat energii w sieciach zakładu energetycznego z uwzględnieniem błędów systemów sprzedaży, diploma thesis. Faculty of Electrical Engineering, Automatics, IT and Electronics of AGH University of Science and Technology, Cracow 1997. [7] The Act of 10 April 1997 Energy law (Journal of Laws No 54 pos. 348 with later amendments – Journal of Laws No 158, pos. 1042 and of 1998, No 94 pos. 594 and No 108 pos. 668).

Zbigniew Lubośny / Gdansk University of Technology Janusz W. Białek / Durham University Authors / Biographies

Zbigniew Lubośny Gdańsk / Polska

Janusz W. Białek Durham / Wielka Brytania

Zbigniew Lubosny graduated from the Gdansk University of Technology (Poland) in 1985. He received his Ph.D. degree in 1991 and D.Sc. degree in 1999 from the same university. He is currently full Professor (since 2004) at the Gdansk University of Technology and Research Fellow at the University of Edinburgh, UK. His fields of interests include mathematical modeling, power system stability and control, artificial intelligence utilization to power system control, wind turbines modeling and control.

Janusz W. Bialek holds M.Eng. (1977) and Ph.D. (1981) degrees in Electrical Engineering from Warsaw University of Technology (Poland), where he worked from 1981 to 1989. From 1989 to 2002 he was with University of Durham, UK. From 2003 to 2009 he held Bert Whittington Chair of Electrical Engineering at the University of Edinburgh, UK. Since 2009 he has held Chair of Electrical Power and Control at Durham University, UK. His research interests are in power system security, liberalization of the electricity power industry, and in power system dynamics.

Analytical derivation of pss parameters For generator with static excitation system

ANALYTICAL DERIVATION OF PSS PARAMETERS FOR GENERATOR WITH STATIC EXCITATION SYSTEM1 Zbigniew Lubośny / Gdansk University of Technology Janusz W. Białek / Durham University

I. NOMENCLATURE Hjj – inertia constant, Eqj – q-axis steady-state internal emf, Iqj – stator current in the q-axis, K1-K6, T3j – parameters of linear model, KPSS, Ta-Tfj – PSS gain and time constants, Pg, Pref, Qgj – generator real, reference and reactive power, Rt, Xtj – step-up transformer resistance and reactance, Rs, Xsj – system resistance and reactance, Rl, Xlj – armature resistance and leakage reactance, Tg, Tmj – electromagnetic and mechanical torque, Ug, Uref, Usj – terminal, reference and infinite bus voltage, Xad, Xaqj – mutual reactance in d and q-axis, Xaduj – unsaturated mutual reactance in d-axis, X’dj – transient reactance in d-axis, Xfj – field circuit reactance, δ j – power angle, ω, ω0 – rotor speed, synchronous speed.

II. INTRODUCTION Problem of damping electromechanical oscillations in electric power systems is not new. Since the 1950s, when power systems started to get bigger and ever more stressed, engineers have been looking for synchronous generator controllers that could improve damping of oscillations. The most popular tool for power system stability enhancement is the power system stabilizer (PSS) which provides an auxiliary control loop to the main automatic voltage regulator (AVR). PSS structure usually follows one of IEEE standards [1]. PSSs are usually of the single-input type with constant parameters (time-invariant) but two-input stabilizers are used too. PSS design is usually based on the compensation of plant frequency characteristics, optimization of defined quality indices, or shifting poles of the considered system to appropriate locations. Abstract This paper presents a methodology for PSS design which results in a PSS producing a nearly pure damping torque component in a wide frequency range. The derivation is based on the Heffron-Phillips single-machine infinite-busbar model and for a generator with static exciter and speedbased PSS. The choice of time constants is very simple and the only parameter still to be optimized is the PSS gain. Effectiveness of the PSS has been confirmed by tests conducted on single- and multi-machine power system model.

1 This work was supported by the Engineering and Physical Sciences Research Council, grant GR/S28082/01 “SUPERGEN: Future Network Technologies”. .

Zbigniew Lubośny / Gdansk University of Technology Janusz W. Białek / Durham University

Other approaches of PSS design have been tried too like e.g. robust control techniques (LQG/LTR, H2, H∞, µ-synthesis), artificial intelligence based techniques (neural networks, fuzzy logic), or adaptive schemes but their practical implementation to the real power systems is so far marginal. Design basis for PSS presently utilized in the power systems were provided in [2]. Practical methodology of PSS design has been proposed in [3] and further developed in [4]. Procedure of PSS design applicable to multi-machine power system was proposed in [5] and further developed in [6]. The practical methods of time-invariant PSS design are using damping torque concept and are based on GEP and P-Vr transfer functions. The GEP(s) is a transfer function between voltage reference of AVR and electrical torque. In case of the real object the transfer function between voltage reference and terminal voltage is measured. The P-Vr is a transfer function between voltage reference and electrical power, i.e., torque when the shaft dynamics of all machines are disabled. The both methodologies were lately compared and discussed in [7]. An interested reader can also consult [8] and [9] for a general description of the need for PSS and its design principles while reports [10] and [11] evaluate different approaches tried. Valuable practical considerations related to PSS design are presented in [12] and [13]. Damping torque concept is related to ideal PSS which, by definition [3], [11], provides damping torque only, i.e. transfer function between rotor speed and electrical torque is a real number over a range of frequencies of the rotor modes. In general, the PSS should provide appropriate damping of electromechanical oscillations, despite it provides a damping torque only or also provides a synchronizing torque. In some circumstances (network configuration, network and machines operating point) it would be valuable to make the PSS to provide some PSS to non-simplified (or real) plant one can expect some i.e. the numerator and synchronizing torque, especially for the low frequency modes, i.e. in case when synchronizing torque produced the and same positions, degradation of its low. ideality, i.e.there weis no achieve PSS introducing by machine and AVR becomes But so far general answer to the question if, when, in what requirement is fulfille amount PSS should provide synchronous torque. slight under-compensation. Tests carried on systems [5] show that non-ideal can and increase torque damping only for the all Despite themulti-machine time-invariant PSS concept and thePSS GEP P- or decrease of given modes in contrary to ideal PSS. Despite this, the existing methods focuses on designing PSS which is search for such Vr tobased years been deeply[12]. andTherefore, with goal ofThe as close ideal as methods possible or issince introducing slighthas under-compensation the paper is the on PSS parameters t to derive equations allowing toan calculate parametersderived of ideal PSS. Because thefor derivation simplified success exploited, analytically equations PSS is based model of synchronous machine while such presented PSS to non-simplified can expect some solution to th parameters computing hasapplying not been so far. (or real) plant oneanalytical degradation of its ideality, i.e. we achieve PSS introducing slight under-compensation. initial assumptions, i.e. Despite the time-invariant PSS concept and the GEP and P-Vr based methods since years has been deeply allow the PSS’s n III. PSS DESIGN and with success exploited, an analytically derived equations for PSS parameters computing •has not been predenominator rank, sented so far.

To achieve the mentioned goal, i.e. ideal PSS, let us • allow the AVR pa consider a model of the single-machine infinite-busbar system, III. PSS DESIGN equations, To achieve the goal, us i.e. assume ideal PSS,that let usthe consider of the single-machine infinitepresented in mentioned Fig. 1. Let planta model is equipped • neglect dynamics busbar system, presented in Fig. 1. Let us assume that the plant is equipped with PSS using rotor speed Dw as with PSS using rotor speed ∆ω as the input. Filter F is an ideal constant, e.g. voltag the input. Filter F is an ideal one. The filter input signal Dh is not defined at this stage. one. The filter input signal ∆η is not defined at this stage. To verify the prop excitation system (IEE

Fig. 1. Single-machine system with AVR and PSS [2] (KD = 0).

The electromagnetic torque ∆Tg can be defined as a function of the rotor angle ∆δ, the reference voltage ∆Vref and

Fig. 2. IEEE type ST1A sta

Let us assume also PSS is as follows:

(s) = K

mowym (PSS), (KD = 0) mowym (PSS), (KD = 0) Rys. 1. Liniowy model układu jednomaszynowego z regulatorem napięcia (RN) i stabilizatorem syste-

Analytical derivation pss parameters Moment elektromagnetyczny jako funkcję kąta of mocy ∆δ, napięcia zadanego mowym (PSS), (KD = 0)∆Me moŜna zdefiniować generator excitation system∆δ, napięcia zadanego 81 Moment elektromagnetyczny ∆Me moŜna For zdefiniować with jako static funkcję kąta mocy generatora ∆Vref oraz prędkości kątowej wirnika generatora ∆ω : generatora ∆Vref oraz prędkości kątowej wirnika generatora ∆ω : Moment elektromagnetyczny ∆can M( se)be moŜna zdefiniować jako funkcję kąta mocy ∆δ, napięcia zadanego The ∆M e =electromagnetic Tδ ( s ) ⋅ ∆δ + TU ( storque ) ⋅ ∆U ref ∆Tg + TPSS ⋅ ∆defined ω (1) as a function of the rotor angle ∆δ, the reference voltage ∆M e speed Tδ ( s )∆ω ⋅ ∆δ: + TU ( s ) ⋅ ∆U ref + TPSS ( s ) ⋅ ∆ω (1) ∆Vref and the rotor generatora ∆V= ref oraz prędkości kątowej wirnika generatora ∆ω : gdzie Tδ(s), TU(s), TPSS(s) są pewnymi transmitancjami zaleŜnymi od parametrów obiektu K1-K6, T3 oraz od (1) od parametrów obiektu K1-K6, T3 oraz od gdzie transmitancjami zaleŜnymi ∆M eTδ=(s), Tδ (T s )U⋅(s), ∆δ T + PSS TU (s) ( s ) ⋅są ∆Upewnymi (1) ref + TPSS ( s ) ⋅ ∆ω transmitancji regulatora napięcia generatora synchronicznego Gex(s) oraz transmitancji stabilizatora transmitancji regulatora napięcia generatora synchronicznego Gex(s) oraz transmitancji stabilizatora (s).(s),CoTPSS istotne, transmitancja stabilizatora systemowego GPSS(s) występujeK1tylko w systemowego GPSST (s) sątransfer pewnymi transmitancjami zaleŜnymi od parametrów -K6on , Tthe δ(s), 3 oraz od where Tgdzie (s), TTV(s), TPSSU(s) are functions that depend on the plant’s parametersobiektu K1PSS -K6(s) , T3występuje and (s). Co istotne, transmitancja stabilizatora systemowego G tylko w G PSSsome δ systemowego (s). funkcji T PSS controller’s transfer functions, defined by G (s) and G (s). What is important here, the PSS transfer function transmitancji regulatora napięcia exgeneratoraPSS synchronicznego Gex(s) oraz transmitancji stabilizatora funkcji PSS(s). G (s) appears in Tthe T (s) transfer function only. PSS Moment elektromagnetyczny wytwarzany przez stabilizator systemowy jest równy: systemowego GPSS PSS(s). Co istotne, transmitancja stabilizatora systemowego GPSS(s) występuje tylko w TheMoment electromagnetic torque produced by the PSS is equal to: elektromagnetyczny wytwarzany przez stabilizator systemowy jest równy: ( ) ( )( 1 + ) K K G s G s sT 2 3 ex PSS R PSS ∆M PSS =funkcji ⋅∆ ω (s). = ∆1ω+(2) TPSS ( s ) T K 2 K 3 Gex ( s )G PSS ( s )( sTR ) )( 1 + ) + sT K K G 5 (2) ∆M PSS = TPSS((1s+) ⋅sT ∆ω = ∆ω (2) R 3 3 6 ex ( s ) 5 Moment elektromagnetyczny wytwarzany przez systemowy jest równy: (1 + sT )(1 + sT ) + K K G stabilizator (s) 3

∀ K K ai G = bi( s )Gtransmitancji (4) Po uwzględnieniu w izaleŜności systemowego i regulatora napięcia bi ( s )(1 + sTR ) stabilizatora (4) ex ai = PSS =1... N , N = M2 3∀ (2) ∆MPo = w ∆ω (2) stabilizatora systemowego i regulatora napięcia TPSS ( s ) ⋅ ∆ω , = i =1... N N M PSS =uwzględnieniu zaleŜności (2) transmitancji After introducing the PSS and(1the transfer functions to (2) the TPSS(s) function can be written in form: + sTAVR R )(1 + sT3 ) + K 3 K 6 Gex ( s )

generatora synchronicznego, transmitancję TPSS(s) (zaleŜność 2) moŜna przedstawić w postaci: tzn. gdy współczynniki wielomianu licznikalicznika i mianownika transmitancji (3), przedstawić znajdujące się na tych (zaleŜność 2) moŜna w postaci: generatora synchronicznego, transmitancję TPSSi (s) tzn. gdy współczynniki wielomianu mianownika transmitancji (3), znajdujące się nasamych tych samych N Po uwzględnieniu 1w zaleŜności (2) transmitancji stabilizatora systemowego i regulatora napięcia i + a s pozycjach w wielomianach, ∑ i będąN sobie równe. Spełnienie warunku (4) powoduje, Ŝe rozwaŜany (3) pozycjach w wielomianach, sobie równe. Spełnienie warunku (4) powoduje, Ŝe rozwaŜany i i =1 1 +K ∑ abędą is TPSS ( ssynchronicznego, = (3) ) = K PSS generatora transmitancję T PSS(s) (zaleŜność 2) moŜna przedstawić w postaci: M = 1 i stabilizator systemowy będzies będzie moment j wytwarzał=tylko Tsystemowy K (3) tłumiący o stałej, tj. niezaleŜnej od częstotliwości stabilizator +) =∑KbPSS PSS1( s M wytwarzał tylko moment tłumiący o stałej, tj. niezaleŜnej od częstotliwości j j j =1 N 1 + ∑ bjs wartości, dla dowolnej częstotliwości elektromechanicznych. + ∑ aj =i 1s i kołysań 1częstotliwości wartości, dla dowolnej kołysań elektromechanicznych. i =1 T s = K = K (3) ( ) PSS PSS M SyntezaSynteza rozwaŜanego stabilizatora sprowadza się zatem dospeed określenia The electromagnetic torque tu ∆Telektromagnetyczny produced bysystemowego the PSS will be in phase with the rotor i.e.parametrów we will Moment (fazor momentu) ∆systemowego TPSS , wytwarzany przez stabilizator systemowy PSS, j PSS tu stabilizatora rozwaŜanego sprowadza się zatem do∆ω, określenia parametrów 1 + ∑ belektromagnetyczny j swhen the transfer function Moment (fazor momentu) ∆ T , wytwarzany przez stabilizator systemowy PSS, PSS (s) will become real. achieve the ideal power system stabilizer, T = 1 j PSS stabilizatora, które spełniają warunek (4). (4). będzie w fazie z prędkością (fazorem prędkości) wirnika generatora ∆ω , tzn. uzyskamy idealny stabilizator stabilizatora, które spełniają warunek The function (3) takes form of a gain K (fazorem when, for prędkości) example, the following requirement is fulfilled: 5 będzie w fazie z prędkością wirnika generatora ∆ω, tzn. uzyskamy idealny stabilizator W celu analitycznego rozwiązania problemu naleŜy przyjąć dodatkowe załoŜenia, a w tym: TPSS (s)elektromagnetyczny będzie liczbą lub funkcją rzeczywistą. systemowy, gdy transmitancja W celu analitycznego rozwiązania problemu naleŜy dodatkowe załoŜenia, a w systemowy tym: Moment (fazor momentu) ∆TPSSprzyjąć , wytwarzany przez stabilizator PSS, T (s) będzie liczbą lub funkcją rzeczywistą. systemowy, gdy transmitancja (4) PSS ∀ a = b (4) i i • dopuścić rząd licznika wyŜszywyŜszy wielomianu mianownika transmitancji ... Nsię , N =wielomianu KniŜ , gdy np. jestmianownika następująca zaleŜność: ZaleŜność (3) staje liczbie rzeczywistej • dopuścić rząd wielomianu licznika niŜ spełniona wielomianu transmitancji będzie wi =1fazie zMrówna prędkością (fazorem prędkości) wirnika generatora ∆ω, tzn. uzyskamy idealny stabilizator K , gdy np. spełniona jest następująca zaleŜność: ZaleŜność (3) staje się równa liczbie rzeczywistej • dopuścić moŜliwość definiowania parametrów regulatora napięcia generatora przez przez wyprowadzone • dopuścić moŜliwość definiowania parametrów regulatora napięcia generatora T (s) będzie liczbą lub funkcją rzeczywistą. systemowy, gdy transmitancja tzn. gdy współczynniki wielomianu licznikaPSSi mianownika transmitancji (3), znajdujące się na tych samych wyprowadzone i.e. the zaleŜności, numerator and denominator coefficients, at the same positions, are equal to each other. tj. wthe celu spełnienia warunku (4) located zaleŜności, tj. w celusobie spełnienia warunku (4), gdy np.torque spełniona jest następująca zaleŜność: ZaleŜność (3) staje się równa rzeczywistej pozycjach w requirement wielomianach, będą Spełnienie warunku (4)only powoduje, Ŝe rozwaŜany When this is fulfilled the liczbie PSSrówne. is providing the K damping for the all frequencies of oscil• pominąć elementy modelu obiektu o małych stałych czasowych, np. przetwornika pomiarowego lations. systemowy • pominąć elementy modelu małycho stałych przetwornika pomiarowego stabilizator będzie wytwarzał tylko obiektu moment otłumiący stałej, tj.czasowych, niezaleŜnej np. od częstotliwości The searchgeneratora. for such PSS means deriving formulas defining the PSS parameters that fulfill requirement (4). napięcia napięcia generatora.kołysań elektromechanicznych. wartości, To finddla andowolnej analyticalczęstotliwości solution to the problem it is necessary to make some initial assumptions, i.e.: • allow PSS’s numerator rank to metody be higher than się the denominator rank, przyjmijmy, W celu weryfikacji zaproponowanej metody syntezy stabilizatora systemowego Ŝe generator Synteza rozwaŜanego tuthestabilizatora systemowego sprowadza zatem do systemowego określenia parametrów W celu weryfikacji zaproponowanej syntezy stabilizatora przyjmijmy, Ŝe generator • allow the AVR parameters to be defined by the derived equations, synchroniczny wyposaŜony jest w statyczny układ wzbudzenia i regulacji napięcia typu IEEE tj. jak tj. jak stabilizatora, spełniają warunek (4). synchroniczny wyposaŜony jestcomponents w statyczny układ wzbudzenia i regulacji napięcia typuST1A, IEEE ST1A, • które neglect dynamics of some with small time constant, e.g. voltage transducer. przedstawiony na method rys. na 2. rys. To verify theprzedstawiony proposed let us a static excitation system (IEEE ST1A W celu analitycznego rozwiązania problemu naleŜy przyjąć dodatkowe załoŜenia, a wmodel), tym: presented in Fig. 2. 2. consider • dopuścić rząd wielomianu licznika wyŜszy niŜ wielomianu mianownika transmitancji

• dopuścić moŜliwość definiowania parametrów regulatora napięcia generatora przez wyprowadzone zaleŜności, tj. w celu spełnienia warunku (4) • pominąć elementy modelu obiektu o małych stałych czasowych, np. przetwornika pomiarowego Rys.generatora. 2.Rys. Model statycznego układuukładu wzbudzenia i regulacji napięcia typu IEEE napięcia 2. Model statycznego wzbudzenia i regulacji napięcia typuST1A IEEE ST1A Fig. 2. IEEE type ST1A static excitation system

W celu weryfikacji zaproponowanej metody syntezy stabilizatora systemowego przyjmijmy, Ŝe generator Let us assume also that the initial transfer function of the PSS is as follows: ZałóŜmy wstępnie transmitancję stabilizatora systemowego o postaci jak (5): synchroniczny wyposaŜony jest wtransmitancję statyczny układ wzbudzenia i regulacji napięcia typu ZałóŜmy wstępnie stabilizatora systemowego o postaci jak IEEE (5): ST1A, tj. jak (1 + sTa )(1 + sTb )(1 + sTc ) przedstawiony naGrys.( 2. (1 + sT )(1 + sTb )(1 + sTc )(5) = K PSS PSS s )G (5) ( ) = K PSS 1 + sTad (5) s PSS 1 + sTd

Additionally, let us neglect the voltage transducerpomiarowego dynamics, bynapięcia assuminggeneratora, that TR = 0. Ponadto pomińmy dynamikę przetwornika przyjmując TR = 0.T = 0. Ponadto pomińmy dynamikę przetwornika pomiarowego napięcia generatora, przyjmując R Dla tak zdefiniowanego obiektu parametry stabilizatora systemowego wytwarzającego tylko Dla tak zdefiniowanego obiektu parametry stabilizatora systemowego wytwarzającego moment tylko moment

tłumiący określone są następującymi zaleŜnościami: tłumiący określone są następującymi zaleŜnościami:

GPSS ( s ) = K PSS

(1 + sTa )(1 + sTb )(1 + sTc ) 1 + sTd

(5)

Zbigniew Lubośny / Gdansk University of Technology W. Białek / Durham University pomiarowego napięcia generatora, przyjmując TR = 0. PonadtoJanusz pomińmy dynamikę przetwornika

Dla tak zdefiniowanego obiektu parametry stabilizatora systemowego wytwarzającego tylko moment For a such defined plant the parameters of the PSS that provides damping torque only are defined by (6): tłumiący określone są następującymi zaleŜnościami:

F , Td = TF (6) Ta = T A , Tb = TB , Tc = 1+ K K K

(6)

T T T T TC = T3 , K F = K 3 K 6 A B , TF T=ATTAB + TB − A B (7) T T Równocześnie parametry muszą być równe: TF = TTA3+ TBnapięcia TC = T3pewne , K FT=3 K ,regulatora − A B generatora (7) 3K6 T3 T3 Simultaneously, some of the AVR parameters have to be defined as follow:

Wówczas zaleŜności (6) i (7) definiują tzw. idealny stabilizator systemowy. Wówczas TzaleŜności (6) i (7) Tdefiniują tzw. idealny stabilizator systemowy. T T T ATB KT K 6, KA B= ,KTK TC = T3 , K FT= = = TTAAT+B T,BT− =AT B + T (7) 3K, Fmiarą − (7) Współczynnik będący momentu tłumiącego wytwarzanego systemowy, jest 3 6 F F A B C 3 T T (7) przez stabilizator 3 T3 T3 tłumiącego wytwarzanego Współczynnik K, będący miarą3 momentu przez stabilizator systemowy, jest wówczas równy: wówczas(6) równy: Wówczas zaleŜności i (7) definiują tzw. idealny stabilizator systemowy. Wówczas (6) i (7) idealny stabilizator systemowy. The Eqs. (6) and (7) zaleŜności define the ideal PSSdefiniują of a giventzw. structure. K 2 K 3 K A K PSS Współczynnik będący miarą momentu tłumiącego wytwarzanego stabilizator systemowy, jest (8) K = K, K K3K A K Gain K which isK, a measure of K the damping torque provided by the isprzez here equal to: stabilizator Współczynnik momentu tłumiącego wytwarzanego przez systemowy, jest PSS (8) PSS, 1 + będący K=6 K A2miarą 3K 1 + K K K 3 6 A wówczas równy: wówczas równy: (8) W rzeczywistości regulator napięcia generatora synchronicznego z rys. 2 dość często występuje w jednej z W rzeczywistości regulator napięcia generatora synchronicznego z rys. 2 dość często występuje w jednej z K 2 K 3 K A K PSS K 2 K 3 K A K PSS (8) = (8) K = następujących Kpostaci (struktur): 1 + K3K6 K A 1 + K K K następujących postaci (struktur): 3 6 A • z pętlą sprzęŜenia zwrotnego (KF ≠ 0) ale bez bloku TGR (Transient Reduction Gain) (TB = TC) z pętlą sprzęŜenia zwrotnego (Kgeneratora ≠ 0) ale bez bloku TGR Reduction (TB =zwTCjednej ) W rzeczywistości regulator napięcia generatora z rys. 2 (Transient dość często występuje w jednej Fsynchronicznego W •rzeczywistości regulator napięcia synchronicznego z rys. 2 dość częstoGain) występuje z • zreal blokiem (TB the ≠ TCAVR, ), alepresented bez pętli in sprzęŜenia zwrotnego (KF =utilized 0). In the powerTGR systems Fig. 2, is also (even often) in one of the following form: następujących (struktur): • postaci z blokiem TGR (T B ≠ TC), ale bez pętli sprzęŜenia zwrotnego (KF = 0). następujących postaci (struktur): • with existing feedback loop (KF ≠ 0) but without transient gain reduction block (TGR) (TB = TC), W pierwszym przypadku, tj. dla generatora synchronicznego z regulatorem napięcia generatora bez bloku • with existing transient gain reduction block (TB ≠TGR Tsynchronicznego ) but without feedback loop (KF(Tnapięcia =B = 0). W pierwszym przypadku, dla generatora z regulatorem • z pętlą sprzęŜenia zwrotnego (K bloku (Transient Reduction Gain) TC) generatora F ≠ 0)tj.ale C bloku • z pętlą sprzęŜenia zwrotnego (Kbez ≠ 0) ale bez TGR (Transient Reduction Gain) (TB = TC) bez bloku F TGR w case, swojeji.e.strukturze, parametry stabilizatora systemowego i regulatora napięcia definiują następujące In the first for synchronous generator equipped with AVR without TGR the PSS and AVR parameters TGR w swojej strukturze, parametry stabilizatora systemowego i regulatora napięcia definiują następujące •are z blokiem TGR (T ≠ T ), ale bez pętli sprzęŜenia zwrotnego (K = 0). B C F • by z blokiem TGRequations (TB ≠ TC), ale bez pętli sprzęŜenia zwrotnego (KF = 0). defined the following zaleŜności: zaleŜności: W pierwszym przypadku,przypadku, tj. dla generatora synchronicznego z regulatorem napięcia generatora bez bloku bez bloku W pierwszym tj. dla generatora synchronicznego z regulatorem napięcia generatora T3 TGR w swojej parametry stabilizatora systemowego i regulatorai regulatora napięcia definiują , TT3c = Td stabilizatora (9) = Tswojej A , Tb =strukturze, parametry TGRTastrukturze, w systemowego napięcianastępujące definiują następujące (9) , Tc = Td (9) 1 A+ ,K 3TKb6=K A Ta = T 1 + K K K 3 6 A zaleŜności:zaleŜności: K F = K 3 K 6T A , TF = T3 6T A , TF = T3 T3 K F = K 3 K T , , T = T = T T =3 Td , T =(9) b a A c , (9) T = Ta =1 +T AKtj.Kdla W drugim przypadku, z regulatoremTGR napięcia generatora z blokiem TGR b Ageneratora synchronicznego c Td 6K In the second i.e. przypadku, for 3synchronous equipped with AVR with but without feedback loop,zthe 1 +tj. K 3dla K 6generator Kgeneratora Wcase, drugim synchronicznego z regulatorem napięcia generatora blokiem TGR A PSSwand AVR strukturze parametersparametry are defined as follows:systemowego i regulatora napięcia definiują zaleŜności: swojej stabilizatora w swojej stabilizatora systemowego i regulatora napięcia definiują zaleŜności: K F = K 3strukturze K 6TK T3 A , =TK F =parametry F 3 K 6T A , TF = T3 (10) B W drugim przypadku, tj. dla Tgeneratora z regulatorem napięcia generatora z blokiem zTGR , Tdrugim ,dla Ta = TA W TTdBgeneratora =synchronicznego TC = T3 + Tsynchronicznego b = T3 , Tc = A (10) z regulatorem napięcia generatora blokiem TGR , (10) Ta = TA , przypadku, Tb =1T+3 K, 3TKc6=Ktj. T = T = T + T A d C 3 A 1 + K K K 3 6 A systemowego i regulatora napięcia definiują zaleŜności: w swojej strukturze parametry parametry stabilizatora w swojej strukturze stabilizatora systemowego i regulatora napięcia definiują zaleŜności: W przypadku drugim, w porównaniu z pierwszym, tj. dla regulatorów definiowanych przez zaleŜności (6) i W przypadku TB drugim,Tw porównaniu z pierwszym, tj. dla regulatorów definiowanych przez zaleŜności (6) i , T,c =(9), , Tthe TIn TA ,second Tb T = T=3 Tcase, + T=cases, in contrary for controllers defined by (6) and (7) or by (9), the time a =the d =B Tprevious C = T,3 T A (10) = to T = T Ti.e. (7) oraz przez stałe definiowane cczasowe a A b1 + K 3 3,KT d TC =zaleŜnością 3 + T A (10)(10) prowadzą do spełniania warunków a1 = b1, K 6 (9), A1+ K K K (7) oraz przez stałe czasowe definiowane zaleŜnością prowadzą dosame spełniania warunków a1 = b1, 3 6 A constants defined by (10) satisfy conditions a1 = b1, a3 = b3 (Eq. (4)) but (10) not satisfy at the time condition = b [zaleŜność (4)], ale nie umoŜliwiają spełnienia warunku a = b . Oznacza to, Ŝe tak określony a 3 means that the PSS produces some synchronizing torque also. 2 Fortunately, 2 a =3b2. This of the (4)],zale nie umoŜliwiają spełnienia definiowanych warunku a2 = przez b2because . Oznacza to, imagiŜe tak adrugim, 3 = b3 [zaleŜność W2 przypadku w porównaniu pierwszym, tj. dla regulatorów zaleŜności (6) i określony drugim, w aporównaniu zwhile pierwszym, tj. dla regulatorów definiowanych przez zaleŜności (6) i narystabilizator part W of Tprzypadku is proportional to – b ≈ T T T is small the imaginary part of T and simultaneously systemowy wytwarza równieŜ, oprócz momentu tłumiącego, pewien moment synchronizujący. PSS 2 2 3 A A PSS stabilizator systemowy wytwarza równieŜ, oprócz momentu tłumiącego, pewien moment synchronizujący. (7) przez (9), torque stałe czasowe definiowane zaleŜnościązaleŜnością (10) prowadzą do spełniania warunkówwarunków a1 = b1, a1 = b1, theoraz synchronizing are stałe small too. (7) oraz przez (9), czasowe definiowane (10) prowadzą do spełniania do a2 - bfunction gdzie be wartość PoniewaŜ jednak część urojona transmitancji Tdenominator PSS jest proporcjonalna 2 ≈ T3TA,should To make the PSS realizable the numerator and the rank of its transfer equal.TA do a b ≈ T PoniewaŜ jednak część urojona transmitancji T PSS jestaproporcjonalna 2Ŝe 2tak 3TA, gdzie wartość TA (4)], ale nie umoŜliwiają spełnienia warunku = b . Oznacza to, określony a3 = b3 [zaleŜność 2 2 (4)], ale nie umoŜliwiają spełnienia warunku to, following Ŝe tak określony adenominator 3 = b3 [zaleŜność 2 = bthe 2. Oznacza Then should be supplemented by two inertia elements, whataleads PSS to the jestthe mała, urojona część transmitancji TPSS i równocześnie moment synchronizujący są równieŜ małe. jest mała, urojona część transmitancji T i równocześnie moment synchronizujący są równieŜ małe. stabilizator systemowysystemowy wytwarza równieŜ, momentu pewien moment PSS form: 7 stabilizator wytwarzaoprócz równieŜ, oprócz tłumiącego, momentu tłumiącego, pewiensynchronizujący. moment synchronizujący. W celu uzyskania realizowalności stabilizatora systemowego rząd wielomianu licznika jego transmitancji W celu uzyskania realizowalnościTPSS stabilizatora systemowego licznika jego do arząd ≈doT3aT2A-, bgdzie wartość TAtransmitancji PoniewaŜ PoniewaŜ jednak część urojona 2 - b2wielomianu jednak TPSS jest proporcjonalna + sTtransmitancji (1część )(urojona 1 + sTb )(1transmitancji + sTc ) jest proporcjonalna 2 ≈ T3TA, gdzie wartość TA a (11) nie moŜe Gbyć Aby to uzyskać, tj. doprowadzić do stanu, w (11) ( większy s ) = K PSS od rzędu wielomianu mianownika. niePSSmoŜe być mianownika. Aby to uzyskać, tj. doprowadzić do stanu, w (1większy + sTd )(1 +od sT )(1i+równocześnie sT wielomianu jest mała, urojona część transmitancji TPSS moment synchronizujący są równieŜ małe. erzędu f ) jest mała, urojona część transmitancji T i równocześnie moment synchronizujący są równieŜ małe. PSS którym rząd wielomianu licznika i mianownika transmitancji stabilizatora systemowego będą równe, którym rząd wielomianu licznika systemowego i mianownikarząd transmitancji stabilizatora systemowego będą równe, W celu uzyskania realizowalności stabilizatora wielomianu licznika jego transmitancji W celu uzyskania realizowalności stabilizatora systemowego rząd wielomianu licznika jego transmitancji i T powinny być na tyle małe, np. T = T < 0,01 s, aby w transmitancji Wartości stałych czasowych T e f e f mianownik transmitancji z zaleŜności (5) do poniŜej: ThenaleŜy valuesuzupełnić of time constants Te and Tf should be chosen small, e.g.postaci Te = Tfjak < 0.01 s, in order not to introduce uzupełnić mianownik transmitancji z zaleŜności do postaci jak poniŜej: do stanu, w nie moŜe nie byćnaleŜy większy odwiększy rzędu wielomianu mianownika. Aby to (5) uzyskać, tj.uzyskać, doprowadzić an significant phase shift to GPSS(s) for frequencies in the electromechanical oscillations range, i.e. 0.1–2.5 do Hz.stanu, w moŜe być od rzędu wielomianu mianownika. Aby to tj. doprowadzić odpowiadających GPSS(s) nie powodować znaczącego przesunięcia fazy z zakresu częstotliwości Introduction of the both small time iconstants practically does not affect the PSSsystemowego effectiveness. będą równe, którym rząd wielomianu licznika mianownika transmitancji stabilizatora którym rząd wielomianu licznika i mianownika transmitancji stabilizatora systemowego będąHz. równe, częstotliwościom kołysań elektromechanicznych w systemie elektroenergetycznym, tj. 0,1–2,5 naleŜy uzupełnić mianownik transmitancji z zaleŜności (5) do postaci jakpostaci poniŜej: naleŜymodyfikacja uzupełnić mianownik transmitancji z zaleŜności (5) do jak poniŜej: PowyŜsza transmitancji stabilizatora systemowego praktycznie nie zmniejsza efektywności rozwaŜanego stabilizatora systemowego.

Analytical derivation of pss parameters For generator with static excitation system

The derived equations allow as to formulate the following remarks: • The PSS and AVR parameters, defined by above Eqs., allowing the PSS to produce damping torque only depend on plant’s operating point, machine data, and external impedance. This confirms common knowledge that parameters of optimal controller of synchronous generator should vary. • The equations show some type of zero/poles cancellation, i.e. some time constants in numerator of the8 PSS transfer function are equal to time constants in denominator of AVR and machine field circuit transfer napięcia (and generatora orazDefinition od stanu of pracy generatora. function opposite). these time constants seems to be intuitive while definition of other 8 time constants and feedback loop(współczynników gain seems not soKobvious. Zmienność parametrów obiektu 1-K6) w funkcji zmienności punktu pracy generatora • Equations (7), (9) and (10) oraz defineodsome parameters of AVR that allow the PSS to perform optimally. That napięcia generatora stanu pracy generatora. i wartości impedancji zewnętrznej jest dyskutowana w pracach [2] i [3] i nie będzie tu powtarzana. can be treated as some disadvantage of the method, but the parameters are often close to the one defiw funkcji zmienności punktu pracy Zmienność parametrów obiektu (współczynników K -K jest Zmienność stałych stabilizatora systemowego w6)funkcji stałej czasowej obiektu T3 generatora ned for existing AVRs.czasowych The AVR parameters defined by (7), (9)1 and (10) allow to proper operation of plant i wartości impedancji zewnętrznej jest dyskutowana w pracach [2] i [3] i nie będzie tu powtarzana. also after PSS disconnection, e.g.Tat open-circuit. względnie mała. Stała czasowa 3 jest mało wraŜliwa na punkt pracy generatora i bardziej wraŜliwa na In case of AVR without feedback loop, dynamic properties of the plant can be independently shaped by Zmienność stałych czasowych stabilizatora systemowego w funkcji stałej czasowej obiektu T3 jest zaleŜności (szczególnie rezystancji) zewnętrznej. stałejloop czasowej Tc w TGR KA andwartość TB, that impedancji are not defined by the derived rules. In case of AVRZmienność with feedback but without the jest mało wraŜliwa na punkt pracy generatora i bardziej wraŜliwa na względnie mała. Stała czasowa T plant’s(6) dynamic canczasowej be independently shaped by K(9) only. this case properties of plant jestInduŜa tylkothe dladynamic punktów pracy generatora i (10)properties oraz stałej Tb w 3zaleŜności A operating at wartość open-circuit relatively highly depend on TA. Thezewnętrznej. smaller value of TA ensures better dynamic w zaleŜności impedancji (szczególnie rezystancji) Zmienność stałejthe czasowej Tc tylko synchronicznego, ulokowanych w pobliŜu granicy stabilności lokalnej obiektu pracującego z properties of the plant. w zaleŜności (9)controller jest duŜa tylko dlaand punktów pracy generatora (6) i time (10) oraz stałej czasowej regulatorem napięcia. • The derived constants of PSS dependTbboth from voltage parameters from plant operating point. synchronicznego, ulokowanych w pobliŜu granicy stabilności lokalnej obiektu pracującego tylko z Zadanie określenia współczynnika stabilizatora jest zadaniem niezaleŜnym The plant parameters variation aswzmocnienia function of operating point systemowego and external impedance is discussed in [2]od regulatorem napięcia. andprzedstawionej [3] and will not metody be repeated here. stałych czasowych stabilizatora. Zadanie to, szczególnie w systemie określania Variation of the PSS time constants that are proportional to T3 is relatively small. T3 is low sensitive to Zadanie określenia współczynnika wzmocnienia systemowego jest zadaniem od wielomaszynowym, nie jest łatwym. Jest ono stabilizatora realizowane w róŜnoraki sposób, a wconstant tym niezaleŜnym w sposób plant load and higher sensitive tozadaniem external impedance (especially to resistance). Variation of time Tc in przedstawionej metody określania stałych czasowych stabilizatora. Zadanie to, szczególnie w systemie (6) pokazany and (10) and Tb in (9) is high only for operating points located close and behind the stability limit of plant powyŜej. equipped wielomaszynowym, with AVR only. nie jest zadaniem łatwym. Jest ono realizowane w róŜnoraki sposób, a w tym w sposób PoniŜej przedstawiono sposób określania współczynnika wzmocnienia stabilizatora The PSS gain definitionprosty is a separate task not related to the time constants definition. The PSSsystemowego. gain definipokazany powyŜej. tion,Dla especially for the multi-machine power system is not easy task, but can be done by utilisation various (s) jest obiektu z rys. 1 równanie ruchu, biorąc pod uwagę (1) i zakładając, Ŝe transmitancja ofTPSS method, e.g. mentioned above. przedstawiono prostysystemowy sposób określania współczynnika wzmocnienia funkcjąPoniŜej rzeczywistą, tj. stabilizator jest idealny, moŜna napisać w postaci: stabilizatora systemowego. Below the simple way of the PSS gain definition is proposed. For plant from Fig. 1 the equation of motion, obiektu z rys. 1 równanie ruchu, biorąc pod uwagę (1) i zakładając, Ŝe transmitancja TPSS(s) jest taking intoDla ω ωthat TPSS(s) transfer function has only a real part (i.e. the PSS is ideal), can Taccount T ω(1) and Tassuming s 2 ∆δ + ( PSS + δD 0 ) s∆δ + δS 0 ∆δ = 0 ( ∆Tm − TV ∆Vref ) (12) be writtenfunkcją 2in H the 2form: Hrzeczywistą, 2 H j tj. stabilizator 2H j systemowy jest idealny, moŜna napisać w postaci: j jω ω TδDω0 TδS ω0 (12) gdzie Ts δ2 ∆S δi +T(δTDPSSsą+zaleŜnymi częstotliwości Tδ(s), definiującymi odpowiednio ) s∆δ + od ∆δ = 0 ( ∆Tm −składowymi TV ∆Vref ) (12) transmitancji 2H j

2 H jω

2H j

momenty synchronizujący i tłumiący, wytwarzane przez maszynę i regulator napięcia generatora. i TδDrównaniem są frequency-dependent zaleŜnymi od częstotliwości składowymi transmitancji definiującymi odpowiednio δ(s), where Tδ Sgdzie and(12) TTδδDS jest are the real and imaginary parts of transfer function Tδ(s) defining Równanie elementu (obiektu) oscylacyjnego 2. rzędu. Dla Ttakiego elementu (obiektu) synchronising and damping components of torque produced by the maszynę machine and AVR. napięcia generatora. momenty synchronizujący i tłumiący, wytwarzane przez i regulator współczynnik wzmocnienia stabilizatora systemowego, przyjmując (8), moŜna obliczyć jakobefunkcję Equation (12) defines a standard oscillatory element. For such element the PSS gain, assuming (8), can calRównanie (12) jest równaniem elementu (obiektu) oscylacyjnego 2. rzędu. Dla takiego elementu (obiektu) culated as the function of the required dampingξratio ξ using: z zaleŜności: wymaganego współczynnika wzmocnienia współczynnik wzmocnienia stabilizatora systemowego, przyjmując (8), moŜna obliczyć jako funkcję 1 + K 3K6 K A ω (13) K PSS = ( 2ξ 2 H jω0 TδS − TδD 0 ) (13) ξ z zaleŜności: wymaganego wzmocnienia ω K 2 K 3 Kwspółczynnika A 1 + K 3 K 6 K AK ω tu nieliniową obiektu, stanu pracy obiektu oraz (13) Kwzmocnienia ( 2PSS ξof2jest H jωplant TδD 0 ) funkcją TheWspółczynnik gain KPSS is a nonlinear function the parameters, stateparametrów and frequency of oscillations. PSS = 0 TδS − K2 K3K A

częstotliwości oscylacji. IV. PSS VERIFICATION IN A SINGLE-MACHINE SYSTEM funkcją parametrów obiektu, stanu pracy obiektu oraz Współczynnik wzmocnienia KPSS jest tu nieliniową For the PSS verification in a single-machine system parameters of synchronous generator marked as G2 in częstotliwości Appendix have been used.oscylacji. Data for that unit has been taken from real generating unit. The unit is equipped with STABILIZATORA SYSTEMOWEGO W UKŁADZIE JEDNOMASZYNOWYM WERYFIKACJA AVRIV. type ST1A without feedback loop. The external impedance, i.e. behind step-up transformer was assumed as equal to Zs = 0.007 + j0.08 p.u. (rated to machine base). Poprawność metody wstępnie w układzie Fig. 3 showszaproponowanej magnitude and angle of TPSSzweryfikowano (s) for various values of reactive power andjednomaszynowym, frequency, when STABILIZATORA SYSTEMOWEGO W UKŁADZIE JEDNOMASZYNOWYM WERYFIKACJA realwykorzystując powerIV. is equal to the rated The PSS and AVR parameters have been recalculated, using (10), at each generator G2one. według danych zawartych w załączniku. Generator synchroniczny jest tu operating Poprawność point. The gainzaproponowanej KPSS was assumed to be equal to one. metody zweryfikowano układzie jednomaszynowym, wyposaŜony w statyczny układ wzbudzenia i regulacji napięcia typuwstępnie ST1A, bezwpętli sprzęŜenia zwrotnego.

wykorzystując generator G2 według danych zawartych w załączniku. Generator synchroniczny jest tu

been recalculated, using (10), at each operating point. The gain become low. In area of lowest values of the TPSS(s) angle, to be equal to one./ Gdansk University of Technology KPSS was assumedZbigniew presented in the Fig., the decrease of damping torque resulting Lubośny Fig. 3 confirms thatW.the PSS/ produces an almost pure from the angle increase is compensated (partly) by increase of Janusz Białek Durham University damping torque as the angle of TPSS(s) is close to zero. Hence the TPSS(s) magnitude. 200 the influence of (a2 – b2) component is very small indeed. That - 0 .3 150 -0 .1 influence in the lowthe frequency range when PSS pure 0 .1 Fig.is3higher confirms that PSS produces an the almost of TPSS(s) is close to 100 damping torque as the angle 0 .3 produces a very small negative synchronizing torque. In the 50 0 .5 zero. Hence the influence of (a2 – b2) component is very small indeed. That influence is higher in the low fre0 .7 high frequency range the PSS produces a very small positive 0 .9 0 Reactive quency range when the PSS produces a very small negative 0synchronizing torque. In the high frequency range synchronizing torque. The magnitude of the transfer function is 0.4 50 0.8 1.2 1.6 2 2.4 2.8 3.2 (p.u.) the PSS produces a very small positive synchronizing torque. The magnitude of the transfer power function is almost 40 almost constant in the whole frequency range but increases 0.9 Frequency (Hz) 0.7 30 constant in the whole frequency range but increases rapidly near the stability limit, i.e. for a capacitive load, rapidly near the stability limit, i.e. for a capacitive load, what 0.5 20 0.3 can becan treated as a positive feature. feature. what be treated as a positive 0.1 10

20 10 0

0 0.4 0.8

0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2

200 150 100 50 0

|Tpss|

- 0 .3 -0 .1 0 .1 0 .3 0 .5 0 .7 0 .9 Reactive 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 power (p.u.) become low. InFrequency area of (Hz) lowest values of the TPSS(s)

angle(Tpss)

Frequency (Hz)

0.05 0.03 0.01 -0.01 -0.03 -0.05

0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2

-0.1 -0.3

Reactive power (p.u.)

0.9 0.7 0.5 0.3 0.1 -0.1 -0.3 Reactive

angle(T pss)

|Tpss|

can be treated as a positive feature.

0 -0.5 -1 -1.5

0 0.4 0.

Fig. 4. Magnitude frequency and reactiv The parameters of th 14.66 s. The paramete Td = 1.72 s, Te = Tf =

angle(T pss)

angle(Tpss)

|Tpss| angle(T pss)

|Tpss|

angle(Tpss)

|Tpss|

angle(T pss)

power (p.u.) 0 Fig. 5 presents 0.9 angle, 4 Frequency (Hz) The gain was cal -0.5 0.7 0.5 presented in the Fig., the decrease of damping torque resulting load and for requi 0.3 0.1 low.of-1In area ofandlowest Tand recalculated, (10), operating The gain n almostbeen pureFig. from the using angle increase is compensated (partly) by increase PSS(s) 3. Transfer function TPSSat(s)each magnitude and point. angle (in radians) asbecome the of function frequency reactivevalues power of for the PSS-0.1 AVRangle, with variable 1.5 -0.3 Transfer function TPSSto(s) magnitude and angle radians) as the assumed bePequal one. presented in-1.5 the Fig., the decrease oftodamping torque resulting Reactive the TPSSand o zero. K Hence (s)tofor magnitude. PSS was = Pgnto . KPSS = 1. Reactive power axis in higherFig. Fig. 3.is reversed in contrary other Figs. show the(in surface. parameters g 0 and 0.4 0.8 1.2 1.6 2.4PSS 2.8 and 3.2 AVR with function of angle frequency reactive power2 for variable T power (p.u.) Fig. 3 confirms that the PSS produces an almost pure from the increase is compensated (partly) by increase of ll indeed. That parameters and by for P(9) g = Pgn. KPSS = 1. Reactive power axis in higher Fig. is In case the PSS and defined byHence (6), (7)reversed or defined the T (s) transfer function angle is equal Frequency (Hz) damping as theofangle of TPSS the TPSSin(s)contrary (s) AVR is close to zero. magnitude. 1.0 when the PSS torque to other Figs.PSS to show the surface. to zero offor(aall at each operating b2) componentand is very small indeed. Thatpoint. influence torque. the In the 2 – frequencies case of the PSS and AVRfrom defined by for (6), the (7) or defined influence is Next higherFig. in the low frequency range when the PSS presents the transfer function TPSS(s)Incomponents calculated (10) time-invariant 0.05 small positive 0.5 Fig. 4.PSS(s) Magnitude and angle (in radians) of TPSS (s)zero as the of by (9) the T transfer function angle is equal to for function all 0.03 produces a very synchronizing torque. In the have been 0.9 sfer function iscontrol scheme. The PSS and AVR time constants computed here for plant operating at the rated 50 small negative = P frequency and reactive power for a time-invariant controller and for P g gn. 0.7 0.01 frequencies and at each operating point. 0.5 positive 40 high operating frequency range PSS produces a very small but increases 1170, TA = 0.01 s, TC = 1.72 s, TB = The parameters of operation the AVR are: K 0.9allows the plant’s -0.01 pointthe and strong system [3], proper atA =the other operating points. 0.3what Next14.66 Fig.s. presents the transfer (s) components 0.7 30 = 1.71 s, Tb = TA , Tc = 0.250.0 s, The parameters of the PSSfunction are: Ta = TT3PSS 0.1 function torque. The magnitude of the transfer is -0.03 ive load,synchronizing what 50 0.5 -0.1 Fig. PSS, ascalculated it canTd =be1.72 expected, for points located far from 20 4 shows that the time-invariant s, T(10) 0.002 s,operating Ktime-invariant at the rated operating point. 0 from the scheme. 0.3Reactive e = Tf =for PSS = 1, calculatedcontrol -0.05 -0.3 40 almost constant10in the whole frequency range but0.1increases 0.9 0 0.4performs 0.8 1.2 1.6 non-ideally, 2 2.4 2.8 3.2 i.e.-0.1 the rated one produces thetime synchronizing torque. The synchronizing 0.7computed The portion PSS and of constants have been 30 Fig. powerwhat (p.u.)some rapidly near the 0stability limit, i.e. for a capacitive 5AVR presents the PSS gain dependence from here frequency. 0.5 -0.3load, Reactive 20 0.3 torque is added here to synchronizing torque produced by machine and AVR. This, in general, is a non-negative for plant operating at the rated operating point and strong 4 0.4 0.8Frequency 1.2 1.6 2(Hz) 2.4 2.8 3.2 Fig. 5. PSS gain and The gain was calculated from (13) for generating unit at rated can be treated as a0positive feature. power (p.u.) 0.1 10 -0.1 operationtorque system [3],and what allows thedamping plant’s proper at the profeature (under-compensated system), especially for the low frequencies when the synchronizing function Tδ(s), calcula load for required ratio equal to ξ = 0.9. -0.3 0 Frequency (Hz) Reactive becomebylow. area of lowest of the TPSS nt. The gain duced angle, other operating points. 0 0.4 0.8 1.2of1.6 2 T2.4 (s) 2.8 angle, 3.2 AVRInand machine canvalues become low. In(s)area of lowest values the presented in the Fig., power (p.u.) The Fig. show PSS Fig. 3. Transfer function TPSSdecrease (s) magnitude and angle torque (in radians) as theFig. 1.5 presented in theof Fig., the of damping resulting 4 shows that the time-invariant PSS,byasincrease it can beof the the decrease damping torque resulting from the angle increase is compensated (partly) Frequency (Hz) gain equal to 20 function of frequency and reactive power for PSS and AVR with variable T δS lmost pure from the angle increase is compensated (partly) by increaseexpected, of for operating points located far from the rated one .3 parameters and for Pg = Pgn. KPSS = 1. Reactive power axis in higher Fig. is than 0.9 for frequ (s) magnitude. KPSS/20 1ero. Hence Tthe PSS TPSS(s) magnitude. performs1.0non-ideally, i.e. produces some portion of the reversed in contrary to other Figs. to show the surface. When reactive 200 ndeed. That synchronizing torque. The synchronizing torque is added here to keep the give - 0 .3 150 In case of the PSS and AVR defined by (6), (7) or defined -0 .1 en the PSS 100 to synchronizing torque produced by machine and AVR. This, suggests that K 0 .1 0.5 PS Reactive by (9) the TPSS(s) transfer function angle 0 .3 is equal to zero for all que. In the in general, is a non-negative feature TδD (under-compensated value needed to k 0 .5 50 power (p.u.) 0 and at each operating point. 0 .7 frequencies all positive system), especially for the low frequencies when the operating point. 0 .9 0 0.9 0.0 Next Fig. presents the transfer function Reactive TPSS(s) 0.7components 0 50 0.4 -0.5 0.8 1.2 1.6 2 2.4 2.8 3.2 function is synchronizing torque produced by AVR and machine can The above calc 0.5 powercontrol (p.u.) 0 0 1 2 3 calculated from (10) for the time-invariant scheme. 0.3 40 -1 Frequency (Hz) t increases 0.9 0.1 0.9 Frequency (Hz) 0.7 computed here -0.5 30 and AVR time constants have been -0.1 0.7 load, what The PSS 0.5 -0.3 0.5 Reactive 20 -1.5 0.3 for plant operating at the rated operating point and strong 0.3 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.20.1 -1 5. PSS gain and the synchronizing and 0.1 Fig. damping components of transfer power (p.u.) -0.1 operation at the system10 [3], what allows the plant’s proper function Tδ(s), calculated at rated operating -0.1 point. 0 -0.3 Reactive -1.5 -0.3 Frequency (Hz) Reactive other operating points. 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 0 0.4 0.8shows 1.2 1.6that 2 2.4 3.2 plant (G2) power (p.u.) powerkeeping (p.u.) The Fig. for 2.8 given the PSS Fig. 4 shows that the time-invariant PSS, as it can be Frequency (Hz) gain equal to Frequency 20 allow (Hz) us to keep the damping ratio not lower expected, operating rated one of Fig. 4. for Magnitude and points angle (inlocated radians)far of from TPSS(s) the as the function than 0.9 for frequencies of electromechanical oscillations. = Pgn. frequencynon-ideally, and reactive power a time-invariant controller and for performs i.e. forproduces some portion of Pgthe When reactive load the plant decreases theand KPSS Fig. 4.TheMagnitude and angle (inare: radians) of T (s) as the function of frequency and reactive power forofa time-invariant controller for required Pg = Pgn. 0.05 = 1170, T = 0.01 s, T = 1.72 s, T = parameters of the AVR K PSS Atorque is added A C B synchronizing torque. The synchronizing here Fig. 4. Magnitude and angle (in radians) of T (s) as the function of PSS to keep the given damping ratio also decreases. 0.03 = are: 1170, = = s,14,66 s. The parameters of the PSS are: Ta = T3 = 1,71 s, Tb =That T , Tcan = The parameters the AVR of are: 1.71s,s,TTCb= = T1,72 14.66 s. The of parameters theKPSS Ta T=A T0.9 3 =0,01 A , Tcs,=T0.25 A B frequency and reactive power for a time-invariant controller and for Pg = Pgn.A c to synchronizing torque produced by machine and AVR. This, 0.7 at the 0.01 = 1.72 s, T = 0.002 s, K = 1, calculated rated operating point. T suggests that K can be defined as equal to the maximum dT es,= TTf = PSS s, = 1,72 T = 0,002 K = 1, calculated at the rated operating point. 0,25 s, PSS 0.5 Reactive = 1170, T = 0.01 s, T = 1.72 s, T = The parameters of the AVR are: K d e f PSS A A C B -0.01 0.3 in general, is a non-negative feature (under-compensated value needed to keep given damping ratio computed for rated 14.66 s. The parameters of the PSS are: Ta = T3 = 1.71 s, Tb = TA , Tc = 0.25 s, 0.1 ower (p.u.) -0.03 Fig. 5 presents the PSS gain-0.1 dependence from frequency. system), especially for the low frequencies when operating = 1.72 s, Te = TThe 0.002 s, Kwas calculated at the rated(13) operating Tthe dfrequency. f =point. PSS = 1, 5 presents the PSS gain dependence from gain calculated from forpoint. generat-0.05TheFig. -0.3 active Reactive gain wastorque calculated from (13) for generating unit atcan rated synchronizing produced by AVR and machine 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 The above calculations were made in simple system (Fig. 1). er (p.u.) power (p.u.) ing load unit0and at rated load and for required damping ratio equal to ξ = 0.9. Fig. 5 presents the PSS gain dependence from frequency. for required damping ratio equal to ξ = 0.9. 0.9 Frequency (Hz) The gain was calculated from (13) for generating unit at rated -0.5 0.7 1.5 n radians) as the 0.5 load and for required damping ratio equal to ξ = 0.9. 0.3 -1 VR with variable T

point. The gain

δS 0.1 -0.1 s in higher Fig. is KPSS-0.3 /20 -1.5function TPSS(s) magnitude and angle Fig. 3. Transfer (in radians) as the Reactive 1.0 0 0.4 1.2 1.6 2 for 2.4PSS 2.8 and 3.2 AVR with function of frequency and 0.8 reactive power variable power (p.u.) parameters and for Pg = Pgn. KPSS = 1. Reactive power axis in higher Fig. is (7) or defined Frequency (Hz) reversed in contrary to other Figs. to show the surface. 0.5 to zero for all TδD

1.5 1.0

TδS

KPSS/20

In case of the PSS and AVR defined by (6), (7) or defined Fig. 5 presents the PSS gain dependence from frequency. 0.5 4. andfunction angle (inangle radians) of TPSS as the of 0.0 by (9) Fig. the T (s) transfer is equal to(s)zero forfunction all s) components PSSMagnitude The gain was calculated from TδD(13) for generating unit at rated frequency power time-invariant 0and 1 for apoint. 2 controller and3 for Pg = Pgn. frequencies and at reactive each operating load and for required damping ratio equal to ξ = 0.9. ntrol scheme. The parameters of the AVR are: KA = 1170, TA = 0.01 s, TC = 1.72 s, TB = Next Fig.s. The presents the transfer (s) s,components Frequency computed here = 1.71 Tb = TA , Tc = 0.250.0 s, 14.66 parameters of the PSSfunction are: (Hz) Ta = TT 3 PSS 1 2 3 s, T = T 0.002 s, K at the rated operating point. 0 T calculated from the time-invariant scheme. d = 1.72 e(10) f =for PSS = 1, calculated control nt and strong active Fig. 5. PSS gain and the synchronizing and damping components of transfer Frequency (Hz) PSSFig. and AVR time constants have been computed here at the ereration (p.u.) The function Tδ(s), calculated at rated operating point. 5 presents the PSS gain dependence from frequency. for plant at the rated operating point and strong Fig.PSS 5. PSS gain and the synchronizing and damping components of transfer The operating gain was calculated from (13) for generating unit at the rated The Fig. shows that for given plant (G2) keeping

Analytical derivation of pss parameters For generator with static excitation system While using the 7 order model of synchronous generator, for As in the single-machine system the turbines wi in the single-machine While using the 7thbecomes order model synchronous for As the damping ratio smallerof and for unit G2 generator, KPSS = 20 were also present in the model. The loads weres 20 the becomes for G2 us to 0.71. This plant is aratio maximum damping ratioand isThe equal to ξ= = constant were present in the m Fig.Kshows that for damping given (G2) keeping thesmaller PSS gain equal to unit 20 admittances. allow keepalso the damping PSS for that plant. ratio achievable not lower than 0.9 for frequencies of electromechanical oscillations. The PSS and AVR time constants for each un is equal to ξ = 0.71. This is a maximum damping ratio constant admittances. When load of the plant decreases the K required to keep the given damping ratio also decreasThe reactive considered PSS has been derived using a simplified calculated in a single-machine model withtime data PSS achievable for that plant. The PSS and AVR es. That can suggests that K can be defined as equal to the maximum value needed to keep given damping model of synchronous generator with taking into account some and AVR, at the rated operating point, PSS considered PSS has been derived using generator a simplified calculated in a single-mac ratio simplifying computed The for rated operating assumptions. The point. further tests have been executed impedance equal to Zs = 0.001+j0.1 p.u. (relat th The above calculations were made in simple system (Fig. 1). While using the 7 order model of and synchroth thsynchronous model of generator with taking into account some generator AVR, at theco using 7 and 13 (multi-mass) order non-linear models of machine rated apparent power). The AVR time nous generator, for K = 20 the damping ratio becomes smaller and for unit G2 is equal to ξ = 0.71. This is PSS simplifying assumptions. The further tests have been executed equal toTab. Zs =VI synchronous generator, AVR – for ST1A type (Fig. 2), PSS – been recalculated impedance to keep original (as in a maximum damping ratio achievable that plant. th th using 7 and 13 (multi-mass) order non-linear models of PSS2A type (Fig. 6), and steam turbine with governor (Fig. machine rated apparent pow TB/TC. The calculated PSS AVR parameters The considered PSS has been derived using a simplified model of synchronous generator with and taking into 13).some Time-invariant and PSSThe with parameters calculated account simplifying AVR assumptions. further tests have been executed using 13threcalculated (multi-mass) to keep o in 2), Tab.PSS I. synchronous generator, AVR – ST1A type (Fig. –7th and been orderfrom non-linear of synchronous generator, – ST1A typegovernor (Fig. 2), PSS – PSS2A type. (Fig. and (10) atmodels ratedtype operating considered. PSS2A (Fig.point 6), were and steam AVR turbine with (Fig. TB/T The 6), calculated PSS C from G3 steam turbine with governor (Fig. 13). Time-invariant AVR and PSS withG1parameters calculated (10) at 13). Time-invariant AVR and PSS with parameters calculated in Tab. I. rated operating point were considered. P +jQ

from (10) at rated operating point were considered.

P5+jQ5 1 Fig. 6. Dual-input PSS (PSS2A type), Tr = 5 s, TF = 0.1 s.

Real power (p.u.)

Fig. 7 shows time response when the plant G2 was subject P6+jQ6 P4+jQ4 to three consecutive step increases of 0.1 p.u. in the infinite G2 busbar voltage. In the considered example, generator has been 6 Fig.initially 6. Dual-input PSS (PSS2A type), Trpower, = 5 s, TPF ==0.1 s. operating at rated real and reactive 0.85 g Fig. 8. Three-machine power system model Fig. 6. Dual-input PSS (PSS2A type), Tr = 5 s, TF = 0,1 s = 0.53 p.u. The step changes of infinite busbar p.u. and QFig. g 7 shows time response when the plant G2 was subject P6+jQtwo There werestep considered 6 Fig. 7 shows time response when the planttoG2 subject to three consecutive increases of cases: 0.1 p.u. voltage moved the operating point finally P = 0.85 p.u. and gwas to three consecutive step increases of 0.1 p.u. in the infinite Case 1: Relatively short andreal low loaded transm in theQinfinite busbar voltage. In the considered example, generator has been operating initially at rated and G2 = -0.85 p.u. (leading power factor), i.e. beyond the stator g The generators operated at approximately rated re busbar voltage. In the considered example, generator has been reactive power, = machine 0,85 j.w.,end Qg = 0,53 heating p.u. Thelimits. step changes of infinite busbar voltage moved the operating current andPthe region g with close tothezero power, with operating initially and reactive power, Pgbeyond = 0.85 point finally Pg = 0.85 p.u. andshows Qat =rated -0.85 p.u. (leading power i.e. stator and thei.e. Fig.reactive 8.current Three-machine power systre Theto plant’s response highreal effectiveness of factor), the g stability margin. machine end p.u. region heating 0.53operating p.u. Thepoint stepbefore changes and Qg =limits. proposed PSS. Despite the each ofof infinite busbar There were considered tw Case System with disconnected line 2-4. Lin The plant’s response shows high effectiveness of the proposed Despite the operating point before applied voltage disturbance is changing, while the controller moved the operating point finallyistotimePg = PSS. 0.85 p.u.2:and 2 with doubled length. Reactive loads almost each invariant of appliedand disturbance changing, whilepoint, the controller is time-invariant and defined atCase rated 1:operating Relatively shortd defined atisrated operating its response for = -0.85 p.u. (leading power factor), i.e. beyond the stator Q g caused that the lines were more loaded in comp point,each its response for each disturbance is very similar. The generators operated at disturbance is very current and thesimilar. machine end region heating limits. case 1. Operating point of generator G3 was clos with close to zero reactiv The plant’s response shows high effectiveness of the one while generator G2, with weakest connection 0.89 stability margin. generators, was operating with almost rated rea proposed PSS. Despite the operating point before each of 0.87 Case 2: System with disc with small reactive power. applied disturbance is changing, while the controller is time0.85 2 with doubled length. Re Fig. 9 illustrates root locus for the considere invariant and defined at rated operating point, its response for 0.83 system, in case 1. caused The lowthat damped are pr the modes lines were each disturbance is very similar. 0.81 The Fig. shows root locus as a functions of theg case 1. Operating point of case when the all gains takes the same value, i.e. 0.79 one while generator G2, wi = KPSS3. The gains are changing from 0 to 30, wi 0.77 Q 0.89 = 0.53 Q = 0.07 Q = -0.39 Q = -0.85 g g g g wasequal operating to 3. Roots relatedgenerators, to the PSS gain to zero a 0.87 0.75 small reactive power. triangle while the with one related to gain equal to 30 0 0.85 2 4 6 8 10 12 14 by square. Fig. 9 illustrates root lo Time (s) In considered case the local modes to 0.83 i tend system, in case 1. M The low Fig. 7. Plant response to three consecutive increases of 0.1 p.u. in the area while frequency of modes which are meas 0.81 TheNtheFig. shows Fig. 7. infinitive Plant response to three consecutive of 0.1 p.u.tointhe thereal infinitive Dashed line corresponds real PSS while theroot locus busbar voltage. Dashed increases line corresponds PSS busbar while voltage. the machine oscillationsto i tend to zero. High increas = 1170, TA = 0,01 s, TC = 1,72 s, TB = 14,66 s. The parameters solid line corresponds to the proposed PSS. The parameters of the AVR are: KA AVR solid line corresponds to the proposed PSS. The parameters of the are: case when the allofgains take 0.79 gain lead model to coherent oscillations the units 1,71 s,s, TTCb = TA , Tcs,=T0,25 s, Td =s.1,72 Te = Tf = 0,002 KPSS = 20. 13th order of synchronous generator, with of the PSS Ta =TTA3 ==0.01 KA =are: 1170, = 1.72 Thes,parameters of thes,PSS B = 14.66 = KPSS3 The gains aretochan M.i becomes equal eac s, Tb = TA , Tc = 0.25 s, Td = 1.72 s, Te = Tf = 0.002 s, KPSS frequency of the modes are: shaft. Ta = T3 = 1.71 multi-mass 0.77 Qg = 0.53 generator, Qg = 0.07 Q = -0.39 Qg = -0.85 = 20. 13th order model of synchronous with multi-massg shaft. 3. Roots related equal to thetoPSz frequencies of thetomodes Ni becomes 0.75 IN MULTI-MACHINE SYSTEM V. PSS VERIFICATION case, maximal damping, by weakest-da triangledefined while the one relat 0 2PSS in 4multi-machine 6 8system10 12 14onfor Verification of the proposed has been carried a 3-machine system shown achievable thisby system becomes equal to about square. V. PSS V ERIFICATION IN M ULTI MACHINE S YSTEM Time (s) in Fig. 8. The system components data and the system initial states are given in Appendix. All the units wereis defined Minimal dampingInin considered the system case the lo equippedVerification with static exciters. As in the PSS single-machine systemsystem the turbines with G3 governors were also present of the proposed in multi-machine (unit’s local mode) which, for inthe PSS gai Fig. 7. Plant response to three consecutive increases of 0.1 p.u. in the area while frequency of m the model. Thecarried loads were as constant admittances. has been on amodeled 3-machine system shown in Fig. 8. The thethe weakest-damped mode. infinitive busbar voltage. Dashed line corresponds to the realbecomes PSS while machine oscillations N tend system components data and to thethe system initial states given of the TheAVR identical solid line corresponds proposed PSS. The are parameters are: value of the each PSS igain coherentofosc in Appendix. All the static exciters. relatively long lead lastingtoovershoots vo TA =units 0.01were s, TC equipped = 1.72 s, Twith of the high PSS andgain KA = 1170, B = 14.66 s. The parameters

frequency of the modes M

Zbigniew Lubośny / Gdansk University of Technology Janusz W. Białek / Durham University

The PSS and AVR time constants for each unit have been calculated in a single-machine model with data of a given generator and AVR, at the rated operating point, with external impedance equal to Zs = 0.001+j0.1 p.u. (related to given machine rated apparent power). The AVR time constant TB has been recalculated to keep original (as in Tab. VII) quotient of TB/TC. The calculated PSS and AVR parameters are presented in Tab. I. 13 G1

G3 P5+jQ5 1

P6+jQ6

P4+jQ4 G2

Rys. 8. Struktura systemu trzymaszynowego Fig. 8. Three-machine power system model

RozwaŜano dwa There were considered twowarianty cases: pracy systemu: • Case Relatively and lowkrótkie loaded itransmission The generators operated at approximately • 1: Wariant 1: short Względnie dość słabolines. obciąŜone linie elektroenergetyczne. Punkty pracy rated real power and with close to zero reactive power, i.e. with relatively low stability margin. generatorów synchronicznych bliskie granicy stabilności lokalnej, ze znamionową generacją mocy • Case 2: System with disconnected line 2-4. Lines 1-6 and 6-2 with doubled length. Reactive loads almost doubled, what caused that the lines were more loaded in comparison to the case 1. Operating point of czynnej generator G3 was close to the rated one while generator G2, with weakest connection to the other gene• Wariant 2: System z wyłączoną linią 2–4. Linie 1–6 i 6–2 o zdwojonej, w stosunku do wariantu 1, rators, was operating with almost rated real power and with small reactive power. długości. ObciąŜenia mocą bierną w węzłach odbiorczych równieŜ zdwojone. Punkt pracy generatora Fig. 9 illustrates root locus for the considered 3-machine system, in case 1. The low damped modes are G3 zbliŜony do znamionowego. Generator G2, najsłabiej związany z resztą systemu presented only. The Fig. shows root locus as a functions of the PSS gain in case when the all gains takes the i małą mocą bierną. same value, elektroenergetycznego, i.e. KPSS1 = KPSS2 = KPSS3.obciąŜony The gains praktycznie are changingznamionową from 0 to 30,mocą withczynną step equal to 3. Roots related to the PSS gain equal to zero are marked by triangle while the one related to gain equal to 30 are marked by square. 9 przedstawia układu trzymaszynowego (zlinearyzowanego) dla are wariantu 1, In Rys. considered case therozmieszczenie local modes Mibiegunów tend to the common area while frequency of modes which measure przy of inter-machine oscillations Ni tylko tend to zero. High increase of thetłumionych PSSs gain lead to coherent oscillaczym prezentowane są tu wartości własne najsłabiej modów. Pokazano tu zaleŜność tions of the units’ rotors, i.e. frequency of the modes Mi becomes equal to each other while frequencies of the połoŜenia biegunów od współczynnika wzmocnienia stabilizatorów systemowych, gdy wartości tych modes Ni becomes equal to zero. In such case, maximal damping, defined by weakest-damped mode, achievwspółczynników dlaequal wszystkich są sobie równe, tj. KPSS1 = KPSS2 = KPSS3. Wartości able for this system becomes to abouttrzech ξ = 0.stabilizatorów 4. Minimal damping in the system is defined by mode M3 (unit’s G3 local mode) which, for the PSS gain KPSSi tych współczynników zmieniają się w przedziale od 0 do 30, z krokiem równym 3. Wartości własne dla > 3, becomes the weakest-damped mode. stabilizatorów systemowych (zero) oznaczone są trójkątami, Thewspółczynnika identical value wzmocnienia of the each PSS gain causes here, relativelyrównego high and 0long lasting overshoots of volt- a dla ages during transient process. To eliminate that effect the PSS gains equal to KPSS1 = 8, KPSS2 = 4, KPSS3 = 26 równego 30-kwadratami. have been chosen. The values allow to keep high damping ratio while keeping the voltage control process reaW prezentowanym przypadku, miarę wzrostu wartości współczynnika stabilizatora sonably good. This effect is visible in Fig. 10,wwhich shows the system response after the linewzmocnienia 2-6 disconnection. Roots locus for system such defined gainsMisi zmierzają presented in 9, in formobszaru, of circles.natomiast In this case the doFig. wspólnego częstotliwości systemowego, modywith kołysań lokalnych damping ratio of the weakest-damped mode is equal to ξ = 0.25. modów będących miarą kołysań międzyobszarowych (międzygeneratorowych) N zmierzają do zera. Triangles in Fig. 9 present also root locus for the PSSs gain equal to zero, in case when i the AVRs are współczynników wzmocnienia stabilizatorów powoduje, kołysania wirników defined byWzrost data presented in Tab. VII, i.e. time constants TB and TCsystemowych have their original values. Ŝe In this case the modes are located practically at the same positions on s-plane like modes calculated for system with the AVRs generatorów stają się koherentne, tzn. częstotliwości modów kołysań lokalnych Mi stają się sobie równe, a time constants defined by (10) (Tab. I). częstotliwości kołysań między obszarowych (międzygeneratorowych) Ni dąŜą do zera. W tym przypadku

tzw. oryginalnym, przedstawionym w tab. VII, tj. z rzeczywistymi (z obiektów rzeczywistych) wartościami stałych czasowych TB i TC. W tym przypadku lokalizacja wartości własnych jest praktycznie identyczna jak Analytical derivation of pss parameters

For generatornapięcia with static excitation system 87 lokalizacja wartości własnych dla obliczenia regulatorów z wartościami parametrów obliczonymi

na podstawie zaleŜności (10) (tab. I). 12

ξ=0.25

8 ω [rad/s]

C3 M2

N3 2

-8

-6

-4 σ [1/s]

-2

Fig. 9. Case 1. Roots locus the 3-machine power system as function of the PSS gain KPSS1 = KPSS2 = KPSS3.

Real power (p.u.)

Fig. 11 presents roots locus, also for case 1, when the gain KPSS3 is changing from 0 to 30, while the rest gains are kept constant, i.e. KPSS1 = 8, KPSS2 = 4. The gain KPSS3 influences modes related mainly to machine G3 (M3, C3) and simultaneously influences modes N2 and N3 that are some measure of oscillations between units G3-G1 and G3-G2. Variation of other modes is very small. In it, change of shape of oscillations between 6units G1 andprocess. G2, defined by N1, that is also small. transient To eliminate effect the PSS gains equal damping. In such a case the weakest-damped mode would be modes M1 and = 8, Fig. KPSS2shows = 4, Kalso 26 the haveroots been locus chosen.pattern The both to KPSS1 The that is here close to M the PSS3 = 3. one presented in the Fig. 9. Mode values allow to keep high damping ratio while keeping the C3 is shifted slightly to the right while mode M3 to the left. 1Mode N3 is characterized by higher than in Fig. 9 voltage control process reasonably good. This effect is visible 0.9 Pg3 infrequency. Fig. 10, which shows the system response after the line 2-6 0.8 disconnection. Pg2 For gain KPSS3 = 15 the mode M3 is locating close to the 0.7 mode M1, which becomes a low-damped mode Roots locus for system with such defined gains is presented Pg1 when K in form ≥ 15.ofThis means that, from point of view of the 0.6 system damping, the gain KPSS3 could be decreased in Fig. 9, PSS3 circles. In this case the damping ratio of 0.5 from 26 to 15 (point the system damping. In such a case the weakestthe weakest-damped mode marked is equal tobyξ =arrow) 0.25. without decreasing 6 0.4 Triangles in Fig. 9 present also root locus for the PSSs gain damped mode would be both modes M1 and M3. 0 0.5 1 1.5 2 2.5 3

s is presented mping ratio of

0.8 0.7 0.6 0.5 0.4

ξ=0.25

Voltage (p.u.)

ω [rad/s]

the PSSs gain 10 0 0.5 1 1.5 2 fined by data Time (s) TC have their C3 ed practically 8 1.1 Vg1 calculated for Vg2 (10) (Tab. I). Fig. 10. System 1.06 response to the outage of line 2-6. M2 1.02

0.94

Voltage (p.u.)

Pg2 Pg1

2.5

Vg1

Vg2

1.06

Vg3

1.02 0.98 0

0.5

1.5

Time (s)

2.5

M1 10

0.5

1.5

Time (s)

Fig. 2 10. System response to the outage of line 2-6. 12

1.1

Fig. 10. System response to the outage of line 2-6.

Vg3

0.98

Time (s)

0.94

2.5

KPSS3 =15

8 ω [rad/s]

Real power (p.u.)

equaldamping. to zero,Ininsuch casea when the weakest-damped AVRs are defined by would data be case the mode S gains equal presented in Tab.MVII, both modes chosen. The M3.time constants TB and TC have their 1 andi.e. original values. In this case the modes are located practically e keeping the 1 at the same positions on s-plane like modes calculated for fect is visible 0.9 Pg3 system with the AVRs time constants defined by (10) (Tab. I). er the line 2-6

C3 M2

Zbigniew Lubośny / Gdansk University of Technology Janusz W. Białek / Durham University

16 12

M1 10

KPSS3 =15

ω [rad/s]

N1 -8

-6

-4 σ [1/s]

N2 -2

Fig. 11. Case 1. Roots in the 3-machine power system as function of the PSS gain KPSS3.trzymaszynowego Rys. 11.locusWariant 1. Lokalizacja biegunów układu

w funkcji współczynnika

wzmocnienia stabilizatora systemowego KPSS3 Finally, Fig. 12 illustrates roots locus for the 3-machine system, in case 2. As previously, the all PSSs gain is equal to each other and changes from 0 to 30. Like in the previous case the circles show root locus for system with various gains (KPSS1= 8, KPSS2= 4, KPSS3= 26). Na zakończenie, rys. 12 for przedstawia połoŜenie modów dlatowariantu 2. 0.4Jak Maximum damping, achievable this system, for KPSSi >> 30, issystemu also equal about ξ = . Forpoprzednio, the PSSs with various gainswzmocnienia the damping ratio of the weakest-damped equal zmieniają to ξ = 0.24, is practiwspółczynniki stabilizatorów systemowych,mode równeissobie, sięwhich od 0 do 30. RównieŜ cally the same value like in the case 1. jakminimal poprzednio, kółka pokazują układu współczynnikami The damping in the system ispołoŜenia defined bybiegunów mode M1, until thedla PSSsystemu gain KPSSi zwillróŜnymi reach 21. Next, the dampingwzmocnienia ratio is very slightly decreased by mode M . stabilizatorów systemowych,4równych odpowiednio KPSS1 = 8, KPSS2 = 4, KPSS3 = 26.

ξ= Maksymalne tłumienie kołysań w tym systemie, osiągane dla KPSSi >> 30, jest równieŜ równe około 17 0,4.12W przypadku systemu z róŜnymi współczynnikami wzmocnienia współczynnik tłumienia najsłabiej M1

tłumionego modu jest równy ξ = 0,24, co jest wartością porównywalną z uzyskaną poprzednio (w ξ=0.24

wariancie 1). 10

Minimalne tłumienie w układzie określa mod M1 do chwili, gdy współczynnik wzmocnienia KPSSi osiąga 8

ω [rad/s]

wartość 21. Dalej współczynnik tłumienia jest słabo ograniczany przez mod M4. M4 M5

M2 4

N3 N1

-8

-6

-4 σ [1/s]

N2 -2

Rys. 12. Wariant 2. Lokalizacja biegunów układu trzymaszynowego w funkcji współczynników

Fig. 12. Case 2. Roots locus the 3-machine power system as function of the PSS gain KPSS1 = KPSS2 = KPSS3

wzmocnienia stabilizatorów systemowych dla przypadku KPSS1 = KPSS2 = KPSS3

Analytical derivation of pss parameters For generator with static excitation system

VI. CONCLUSIONS The paper presents way of deriving equations that allow to calculate parameters of PSS that produces a damping torque only in a wide frequency range. The derivation is based on the 3rd order single-machine infinite-busbar model and is applied here for generator with static exciter and speed-based PSS. Because the method is the AVR structure sensitive, as result, three sets of equations allowing to calculate PSS parameters for three various structures of AVR are presented. The PSS parameters defined by proposed equations depend on plant data, AVR parameters, system operating point and external impedance. Because of the latter two, the PSS parameters should vary during plant operation but tests have proved that the proposed PSS in form of a time-invariant controller performs almost equally well. The PSS parameters are related to some of the AVR parameters and therefore should be set simultaneously. Advantage of the proposed methodology is simplicity of the PSS design. PSS time constants can be calculated directly, using a single-machine steady-state model, without any iterative optimization process. Simulations have shown that the values derived in a single-machine system (by applying the proposed equations) are valid also in a multi-machine system. The proposed method has been verified for large units operating in transmission system and for smaller units operating in distribution systems (results not presented here) giving in the all cases good results. The method seems to be especially suited for units operating in the distribution systems because the distribution systems operates as radial and the transmission system, from point of view of such units, can be treated as infinite busbar. Then solution achieved for the single-machine system directly match to generating unit operating in the distribution system. Low amount and accessibility of data that is necessary to calculate the PSS (and AVR) parameters allow us to implement the derived equations in any digital controller of synchronous generator. In such a case the PSS parameters and some AVR parameters can be calculated just by the synchronous generator controller. The equations proposed in the paper allow us to define PSS that effectiveness is similar to effectiveness of the well tuned PSS, which parameters are defined by using GEP or P-Vr methodology. This is because the all mentioned methods are based on damping torque concept and, especially because they utilize the same structure of PSS, which in fact defines limits of such PSS efficiency. VIII. APPENDIX A. Linear model of single-machine infinite busbar system X’d = Xl+Xad− Xad×Xad/Xf RT = Rl+Rt+Rs,

XTq = Xq+Xt+Xs,

XTd = X’d+Xt+Xs

D = RT×RT+XTd×XTq m1 = Vs(XTq×sinδ−RT×cosδ)/D, m2 = XTq×Xad/(D×Xf),

n1 = Vs (RT×sinδ+XTd×cosδ)/D

n2 = RT×Xad/(D×Xf)

K1 = Eq×n1+Iq×(Xq-X’d)m1 K2 = Xad[RT×Eq/D+(1+XTq×(Xq− X’d)/D)Iq]/Xf K3 = Xf/[Xadu×(1+(Xd−X’d)×XTq/D)],

K4 = Xadu×Xad×m1/Xf

K5 = (-Rl×m1+Xq×n1) sinδ+(−Rl×n1-X’d×m1)cosδ K6 = (−Rl×m2+Xq×n2)sinδ+[−Rl×n2-X’d×m2+(X’d−Xl)/(Xf-Xad)]cosδ T3 = Xf/[ω0×Rf(1+XTq(Xd−X’d)/D)]

Zbigniew Lubośny / Gdansk University of Technology Janusz W. Białek / Durham University

B. Single- and multi-machine models data TABLE I PSS (IEEE Type PSS2A) AND avr dATA

Parameter

Unit

0,02

Tb = TA

1,929

1,749

1,679

0,318

0,346

0,394

1,949

1,769

1,699

Te = Tf

0,002

–

730

1170

400

17,25

15,04

8,496

1,949

1,769

1,699

Case 1. Transmission lines: Un = 400 kV, Z’ = 0,006 + j0,4 Ω/km, B’ = 3,52 μS/km, l15 = 100 km, l53 = 150 km, l34 = 140 km, l24 = 120 km, l26 = 130 km, l16 = 110 km. Loads: S4 = S5 = S6 = 200 + j100 MVA TABLE II System Initial Nodal Voltages [p.u.] in Case 1

Mag.

1,042

1,036

1,035

Angle

0°

2,9°

1,7°

0,5°

–1,0°

–0,4°

TABLE III Synchronous Generators Initial State in case 1

Parameter

Unit

Sgi

MVA

105,4 - j8,3

340,7 + j5,1

200,5 – j31,2

Ugi

j.w.

1,032

1,018

δgi

deg.

49,7

62,5

68,3

Case 2. Transmission lines: Un = 400 kV, Z’ = 0,006 + j0,4 Ω/km, B’ = 3,52 μS/km, l15 = 100 km, l53 = 150 km, l34 = 140 km, l24 = wyłączona, l26 = 260 km, l16 = 220 km. Loads: S4 = 200 + j150 MVA, S5 = 200 + j200 MVA, S6 = 200 + j200 MVA TABLE IV System Initial Nodal Voltages [p.u.] in case 2

Mag.

1,042

1,000

1,002

1,000

Angle

0°

16,2°

–2,8°

–6,6°

–2,8°

4,1°

TABLE V Synchronous Generators Initial State in case 2

Parameter

Unit

Sgi

MVA

74,4 + j67,5

340,7 + j38,3

200,5 + j127,1

Ugi

j.w.

1,10

1,05

1,11

δgi

deg.

22,8

55,6

38,8

Analytical derivation of pss parameters For generator with static excitation system

TABLE VI Synchronous Generator Parameters

Parameter

Unit

Sgn = Sbase

MVA

150

426

235,3

Pgn

125

360

200

Ugn = Ubase

13,8

15,75

–

1,84

2,6

2,19

X’d

–

0,305

0,33

0,324

X”d

–

0,22

0,235

0,217

–

1,66

2,48

2,1

X’q

–

0,49

0,53

0,513

X”q

–

0,22

0,235

0,217

–

0,15

0,199

0,194

–

0,0013

0,0016

0,0015

T’d0

7,8

9,2

7,62

T”d0

0,145

0,042

0,209

T’q0

0,88

1,095

1,54

T”q0

0,071

0,065

0,305

–

0,243

0,292

0,163

S12

–

0,48

0,883

0,207

2Hj

7,8

6,45

10,0

–

0,1386

0,1534

0,1443

–

0,0056

0,0034

0,004

Parameter

Unit

0,02

–

730

1170

400

0,02

17,7

VIMAX/VIMIN

–

0,15/–0,15

0,15/-0,15

VRMAX/VRMIN

–

5,9/–5,9

7,1/–5,0

6/-5,2

–

0,08

0,06

0,07

–

0,04

TABLE VII. AVR Data (IEEE Type ST1A)

Zbigniew Lubośny / Gdansk University of Technology Janusz W. Białek / Durham University

TABLE VIII Turbine Controllers Data

Parameter

Unit

–

TGHP, opening

2,0

TGHP, closing

0,05

TGIP, opening

2,7

TGIP, closing

0,15

Parameter

Unit

THP

0,1

s 0,1 s 0,4 – 6 – 0,3 – 0,3

0,4

0,2

0,3

0,35

0,3

0,45

0,4

TABLE IX Turbines Data

miary s s s – –

TLP 0,1 TRH 0,4 KHP 7 KMP 0,2 KLP 0,35

0,1 0,4 10 0,3 0,3

HP, MP, LP 0,4 – high, medium – Indexes: 0,45 0,4 and low pressure, RH – reheater

y: HP, MP, LP – wysoko-, średnio- i niskopręŜny, RH – przegrzewacz międzystopniowy. Pref wg

KI 1 sTI

Σ 1

YHP 1 1+sTGHP YIP 1 1+sTGIP

wref

3. Model Fig. regulatora turbiny (YHPmodel , YIP(Y– , połoŜenie zaworówvalve wysokopręŜnych intercepcyjnych 13. Steam turbine governor YIP – high and interception position, TGHP , TGIP – itime constant of high- and intercept valve) HP y, TGHP, TGIP – stałe czasowe zaworów wysokopręŜnych i intercepcyjnych)

grafia

E Std 421.5-1992: IEE Recommended Practice for Excitation System Models for Power System

ty Studies, IEEE, New York 1992, ISBN 1–55937–218–4.

lo de F.P., Concordia C., Concepts of Synchronous Machine Stability as Affected by Excitation

ol, IEEE Trans. Power Appar. Syst., vol. 88, 1969, s. 316–329.

en E.V., Swann D.A., Applying Power System Stabilizer, IEEE Trans. Power Appar. Syst., vol. 100,

s. 3017–3046.

lo de F.P., Czuba J.S., Rushe P.A., Willis J.R., Developments in Application of Stabilising Measures

gh Excitation Control, Paper Ref. 38-05, CIGRE Session 1986.

Analytical derivation of pss parameters For generator with static excitation system

LITERATURE 1. IEEE Std 421.5-1992: IEE Recommended Practice for Excitation System Models for Power System Stability Studies, IEEE, New York 1992, ISBN 1–55937–218–4. 2. Mello de F.P., Concordia C., Concepts of Synchronous Machine Stability as Affected by Excitation Control, IEEE Trans. Power Appar. Syst., vol. 88, 1969, s. 316–329. 3. Larsen E.V., Swann D.A., Applying Power System Stabilizer, IEEE Trans. Power Appar. Syst., vol. 100, 1981, s. 3017–3046. 4. Mello de F.P., Czuba J.S., Rushe P.A., Willis J.R., Developments in Application of Stabilising Measures Through Excitation Control, Paper Ref. 38-05, CIGRE Session 1986. 5. Gibbard M.J., Co-ordinated design of multimachine power system stabilizers based on damping torque concept, Proc. Inst. Elect. Eng. C, vol. 135, no. 4, July 1988, s. 276–284. 6. Gibbard M.J., Robust Design of Fixed-parameter Power System Stabilisers over a Wide Range of Operating Conditions, IEEE Trans. Power Syst., vol. 6, no. 2, May 1991, s. 794–800. 7. Gibbard M.J., Vowles D.J., Reconciliation of Methods of Compensation for PSSs in Multimachine System, IEEE Trans. Power Syst., vol. 19, no. 1, February 2004, s. 463–472. 8. Kundur P., Power system stability and control, New York: McGraw–Hill, 1994, s. 761. 9. Machowski J., Bialek J., Bumby J.R., Power System Dynamics and Stability, New York: John Wiley and Sons, 1997, s. 291. 10. CIGRE Task Force 38.02.16, Impact of Interactions among Power Systems, Paris, August 2000. 11. CIGRE Task Force 38.01.07, Analysis and Control of Power System Oscillations, Paris, December 1996. 12. Lee D.C., Kundur P., Advanced Excitation Controls for Power System Stability Enhancement, Paper Ref., no 38–01, CIGRE Session 1986. 13. Murdoch Dr.A., Venkataraman S., Lawson R.A., Pearson W.R., Integral of Accelerating Power Type PSS. Part 1 – Theory, Design, and Tuning Methodology. Part 2 – Field Testing and Performance Verification, IEEE Trans. on Energy Conv., vol. 14, no. 4, December 1999, s. 1658–1672.

Ryszard Michniewski / ENERGA-OPERATOR S.A. Toruń Branch

Author / Biographie

Ryszard Michniewski Toruń / Polska Ryszard Michniewski obtained his diploma at the Electrical Engineering Faculty at the Poznań University of Technology. He began his professional career as a constructor in Pomorskie Zakłady Wytwórcze Aparatury Niskiego Napięcia in Toruń. Later he worked as production maintenance engineer in Pomorskie Zakłady Przemysłu Wapiennego Bielawy. Since 1962, he has worked at various positions at Zakłady Energetyczne in Toruń, till his retirement in 2004. Today, he is involved in training and implementation of live working technique (PPN technology) projects on overhead high and extra high voltage lines in ENERGA-OPERATOR SA He is a member of Polskie Towarzystwo Przesyłu i Rozdziału Energii Elektrycznej [Polish Association of Electrical Power Transmission and Distribution], member of Polski Komitet Bezpieczeństwa w Energetyce [Polish Energy Security Committee] and Association of Polish Electrical Engineers (SEP).

PPN - live conductor operations on 400 kv, 220 kv and 110 kv overhead transmission and distribution lines in ENERGA-OPERATOR S.A., Toruń Branch

PPN - LIVE CONDUCTOR OPERATIONS ON 400 KV, 220 KV AND 110 KV OVERHEAD TRANSMISSION AND DISTRIBUTION LINES IN ENERGA-OPERATOR S.A. TORUŃ BRANCH Ryszard Michniewski / ENERGA-OPERATOR S.A. Toruń Branch

The history of live-working techniques (PPN) on high and extra high voltage overhead lines in ENERGAOPERATOR S.A. Toruń Branch dates back to 1933 when the first operations applying the PPN technology took place in Pomorska Elektrownia Krajowa Gródek (previously ENERGA-OPERATOR S.A., Toruń Branch ) on the 60 kV line Gródek – Gdynia. Revival of PPN operations on overhead transmission lines took place in 1990 on 400 kV lines using equipment and technologies purchased in the former German Democratic Republic. 1992 marked the beginning of performing PPN operations on straight line poles and straight and transposition line poles for 220 kV based on technologies developed in Zakład Energetyczny in Toruń in cooperation with the Occupational Work Safety Section at the Institute of Power Engineering in Gliwice In 2008, ENERGAOPERATOR S.A., Toruń Branch developed and implemented a technology for replacing insulators and insulator assemblies on anchor poles and anchor and angle poles. Number of operations on lines: 400 kV Poles

220 kV Poles

Anchor and angle poles

Straight line poles

Straight and transposition poles

Anchor and angle poles

245

624

260

Total number of operations

1153

Table 1 shows the number of PPN technology operations on 400kV and 220kV lines in the period 1990 to the end of 2008.

Table 2 shows Year operations in particular years. 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Razem

Line 400 kV 2 5 7 2 2 6 5 26 4 1 1 8 1 1 174 199 194 128 103

220 kV 2 35 94 20 16 1 3 2 9 1 3 9 2 1 20 34 32

2 5 9 37 96 26 21 27 7 3 10 9 4 10 176 200 214 162 135

869

284

1153

Total

Abstract The paper presents the short history of hotline operations (PPN) on 400 kV, 220 kV overhead transmission lines and 110 kV lines from the first PPN operations performed by ENERGA-OPERATOR S.A. Toruń Branch to the end of 2008. The volume of work performed on the lines is shown and the kinds of operations. The paper describes the methodology and technologies applied during the operations. Pictures are included showing operations on 400 kV, 220 kV, 110 kV and the design of the derrick for transporting the fitter to the 400 kV hotlines and the insulator string to the pole lines. The operations

applying PPN technology performed on 400 kV, 220 kV and 110 kV lines provided grounds for conclusions regarding the reduction of line power loss, i.e. the positive economic and environmental impact of the PPN technology.

Ryszard Michniewski / ENERGA-OPERATOR S.A. Toruń Branch

96 1

Photo. 1. PPN operations on 400 kV – single circuit line pole, suspension type Photo. 2. PPN operations on 400 kV – suspension type ŁPV-400 – work on platform

Photo. 3. PPN on 400 kV line 400 – fitter reaching hot line Photo. 4. PPN on 400 kV line suspension type ŁO2 – mounting the cradle for the insulator string

Photo. 5. PPN on 400 kV line, suspension type ŁO2-400 – disconnecting the insulator string Phot. 6. PPN on 400 kV, suspension type ŁO2 – hoisting the insulator string

Phot. 7. PPN on 400 kV line, suspension type ŁO2-400 – hoisting the insulator assembly

PPN - live conductor operations on 400 kv, 220 kv and 110 kv overhead transmission and distribution lines in ENERGA-OPERATOR S.A., ToruĹ&#x201E; Branch

PPN operations on 400kV lines are performed against a written request with a statement from all members of the team of their physical and psychic fitness to perform the job. The work is performed by a team of nine members: three fitters work on the pole cross-arm, one on the hotline with the rest at the pole mount, the foreman supervises the performance procedure. Work on a 220kV line is performed by a team of eight with allocation of duties similar as in the case of a 400 kV line except for the fact that two fitters work on the cross-arm. The live working technique on 400 kV anchor poles according to the German technology was both labour consuming and dangerous (fitters refused to apply this technology). In 2006, ENERGA-OPERATOR S.A. ToruĹ&#x201E; Branch developed a new technology for PPN operations on 400 kV anchor poles and anchor and angle poles. According to the new technology, transport of fitters to the hotline and transport of the insulator string is performed with the use of a two element insulation derrick linked by a pulley block with the insulation ropes. The derrick boom is made of two parts (can also be a three part structure) of relevant mechanical and electric strength. The boom is topped by a special metal head, supported on conductor lines, used to hoist the fitter to the hotline using an insulation ladder and an electric driven winch. Fig. 1. Derrick transporting fitter to the hotline

Head top on mast Hoisting tackle

Block

Mounting grip for top rack bar Angle iron handle Grip with transporting supporter Derrick mast

Insulation stick connecter on boom Derrick boom

Boom connector

Travelling grip on boom

Derrick and insulation ladder connector Derrick mount

Support, cotter pin Insulation ladder

Hoisting tackle

Fig. 2. Derrick transporting replaced insulator string

Block

Insulation stick connecter on boom

Travelling grip on boom

Angle iron handle Derrick mast

Derrick boom

Boom connector

Derrick and insulation ladder connector derrick mount Support, cotter pin

Insulation ladder

Ryszard Michniewski / ENERGA-OPERATOR S.A. Toruń Branch

Block

Insulation stick connecter on boom Derrick boom

Boom connector

Travelling grip on boom Derrick and insulation ladder connector 800

Support, cotter pin Insulation ladder

Segment part 1 – diameter 110 4800

Segment part 2 – diameter 110 Segment part 3 2500

Segment part 3 – dimension in (mm) 500 3.1. 800 3.2. 3.3. 900 3.4. 1100 3.5. 1200

Fig. 3. Derrick – selecting boom length relevant for the line bend angle

An application to the Patent Office of the Republic of Poland was submitted in 2007 for PPN operations on anchor poles and anchor and angle poles to obtain patent protection for the new technology. It is entered under the number P 382278. In 2008, ENERGA-OPERATOR SA Toruń Branch developed and implemented the new technology for the live working technique on 220 kV anchor poles and anchor and angle pole lines, suspension type ŁO2 and ŁO3. Development of the technology was quite difficult because most 220 kV lines base on VKLF 75/16 and VKLS 75/21 type long rod insulators, which have a high damage rate. For this reason conductors and insulator strings cannot be used in hoisting the fitter to the hot line and for fitter’s operations on the hotline from the conductor side. To enable the replacement of insulator and insulation assemblies, suspension type ŁO2 and ŁO3, (long rod insulation), the control of tension line must be ensured prior to the operation. Special holders/clamps have been constructed (made of steel, aluminium or plastic) placed on the strain yoke of insulator string on the side of the conductor and on the side of the pole structure. Thanks to these clamps for insulation sticks and pull, the line strain functions are reallocated and allow for the replacement of insulators and assemblies. The fitter is transported to the hotline with use of an insulated ladder, which is hoisted with an insulation system comprising a six meter long and ø 75 mm insulation stick, metal cable head, insulation rollers and angle clamps. The insulation system is fastened in two points to the lower angle bar of the pole cross-arm. Operations on the insulator string from the conductor side are performed by the operator on the insulated ladder, connected to the insulation assembly. The insulation head is supported during the operation by the insulation derrick boom (for better bracing). An application for patenting this technology is being at present processed by the Polish Patent Office.

PPN - live conductor operations on 400 kv, 220 kv and 110 kv overhead transmission and distribution lines in ENERGA-OPERATOR S.A., Toruń Branch

Phot. 8, 9. PPN operations on 220 kV – straight line poles

Phot. 10, 11. PPN operations on 220 kV - single and double circuit line suspension type ŁPO-220 and ŁP2-220

Phot. 12. PPN operations on 220 kV - double circuit line poles, suspension type ŁP2-220

Ryszard Michniewski / ENERGA-OPERATOR S.A. Toruń Branch

100

Table 3 presents the scope of works on 400kV and 220kV lines applying PPN technology. No.

Year

1993–1995

Line

Scope of operations

220 kV line Włocławek Azoty – Pątnów

Replacement of 318 VKLF 75/16 on straight line poles and straight line and transposition poles

2004

Double circuit 400kV line Gdańsk Błonia – Żarnowiec

Replacement of 141 slings on straight line poles

2005

400 kV line Grudziądz Węgrowo – Płock

Replacement of 74 PS16B insulators on straight line poles and repair of 73 surge arrester bridges

2005

400 kV line Krajnik – Dunowo

Replacement of 74 PS16B insulators on 57 straight line poles

2006

400 kV line Dunowo – Słupsk

Replacement of 100 PS16A insulators on straight line poles and 9 PS22A on anchor poles

6 7

2006 2006

400 kV line Słupsk – Żarnowiec

Replacement of 38 PS22A insulators in 35 rows, suspension type ŁO2 and ŁO3

220 kV line Dunowo – Żydowo

Replacement of 21 PS16B insulators on straight line poles

2006

400 kV line Krajnik – Dunowo

Replacement of 8 PS22A insulators, suspension type ŁO2 and ŁO3, and replacement of 28 insulators PS16B, suspension type ŁP and ŁPV

2007

400 kV line Połaniec – Rzeszów

Replacement of 20 insulators, suspension type ŁO2 and ŁO3

2007

400 kV line Krajnik – Dunowo

Replacement of 121 PS22A insulators, suspension type ŁO2 and ŁO3 and 24 PS16B insulators, suspension type ŁP and ŁPV

2007

220 kV line Olsztyn – Ostrołęka

2008

400 kV line Krajnik – Dunowo

2008

220 kV line Olsztyn – Ostrołęka

Replacement of 114 insulators LP 75/17 assembly, suspension type ŁPO on straight line and transposition poles Replacement of 26 insulators PS16B, suspension types ŁP and ŁPV on straight line poles and replacement of 86 insulators PS22A, suspension type ŁO2 and ŁO3 on anchor lines, in total 110 pieces in 103 rows Replacement of 30 insulators LP 75/17 assembly, suspension type ŁPO, and 48 assemblies suspension type ŁO2

The first PPN operations on overhead transmission lines took place in 1998 on 110 kV lines. Up to date, the only company applying PPN technology for this voltage is ENERGA-OPERATOR SA, Toruń Branch . Operations on overhead 110 kV transmission lines apply two methods. • remote method • hotline method – developed by ENERGA-OPERATOR SA, Toruń Branch in 2007. Remote operations on 110 kV straight lines with use of insulations sticks with heads, which hold the appropriate tools (their dimensions cannot exceed 300x300x150 mm), and a pulley block with insulation ropes. PPN operations on anchor and angle poles are performed with the help of; a two part insulation derrick mounted on the pole shaft, insulation pull with hooks placed on the conductor, and by the anchor clamp and insulation sticks holding relevant tools. PPN operations on 110 kV straight lines are performed by a team of six. Two fitters work on the pole structure, four on the pole mount, the foreman supervises the performance procedure. PPN operations on anchor poles are performed by a team of seven. Three fitters work on the pole structure, four on the pole mount. The work is performed at a written request for the service supplemented by a statement of the team members confirming their physical and psychic fitness to perform the operation applying PPN technology. Table 4 shows the number of operations performed by ENERGA-OPERATOR SA, Toruń Branch on 110 kV lines. Table 4.

Year 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Razem

Number of PPN operations 68 361 294 22 250 87 353 835 931 836 740 4777

Number of operations on poles Straight poles 51 346 250 19 231 1 208 295 477 349 210 2437

Straight and transition poles 17 15 44 3 19 19 45 3 12 177

Anchor and angle poles 86 145 521 409 484 518 2163

Number of replaced insulators 98 403 447 25 275 104 479 1401 1291 1358 1331 7212

Average time required for insulator replacement on poles Anchor and Straight poles angle poles 50 min 53 min 1 h 12 min 60 min 50 min 1 h 15 min 1 h 50 min 44 min 1 h 17 min 50 min 1h 48 min 59 min 48 min 58 min 46 min 60 min

PPN - live conductor operations on 400 kv, 220 kv and 110 kv overhead transmission and distribution lines in ENERGA-OPERATOR S.A., Toruń Branch

Phot. 13. Replacing an insulator suspension type ŁP-110 on straight line pole Phot. 14. Replacing an insulator suspension type ŁPO-110 on straight and transition pole

Phot. 15. Replacing an insulator suspension type ŁPO-110 double circuit hot line Phot. 16. Replacing an insulator on suspension type ŁP2-110 on straight and transition pole

Phot. 17, 18. Replacing an insulator suspension type ŁPO-110

Phot. 19, 20. Replacing an insulator suspension type ŁO2-110

101

Ryszard Michniewski / ENERGA-OPERATOR S.A. Toruń Branch

102

Economic and environmental effects of applying the PPN technology in operational and repair works are presented in Table 5 (for 220 kV and 400 kV lines), and in Table 6 the effects of application on 110 kV lines. Table 5 Disconnected transmission system element Year 2004 l. 400 kV Gdańsk Błonia – Żarnowiec Year 2005 l. 400 kV Krajnik – Dunowo l. 400 kV Grudziądz – Płock Year 2006 l. 400 kV Dunowo – Słupsk l. 400 kV Słupsk – Żarnowiec l. 400 kV Krajnik – Dunowo Year 2007 l. 400 kV Krajnik – Dunowo l. 220 kV Olsztyn – Ostrołęka Year 2008 l. 220 kV Olsztyn – Ostrołęka l. 400 kV Krajnik – Dunowo

Economic effects Economic Loss increase effect of loss Not emitted to the atmosphere resulting from Coal not reduction disconnecting burnt SO2 NOx CO2 (thousand the line (MWh) (t) (t) (t) (t) PLN)

Pył (t)

Hours on hot line

984,4

115,2

460

962,7

7,85

2,23

0,5

7 852

919,7

3 667

7 685

62,6

17,82

4,09

156

11 606

1 357,9

5 420

11 351

92,6

26,3

6,05

192

1 829

214

854,1

1 789

14,6

4,15

0,95

170

845

98,8

394,6

826,4

6,74

1,92

0, 44

141

3 323

388,8

1 552

3 250

26,5

7,54

1,73

16 173

2 102,5

7 552,8

15 817

119,4

36,7

8,4

316

487, 5

63,4

227,6

476,8

3,9

1,1

0,254

248

35,0

115,8

242,5

1,98

0,56

0,13

14 569

2 040

6 803,7

14 248,5

116,2

7,6

285

57 917,0

7 335,3

27 048,0

56 649,0

452,4

131,3

30,144

1 554

Table 6 Lp.

Specification of adverse effects in the case of replacing insulators applying the traditional method, i.e. disconnecting 110 kV

110 kV line Pątnów –Piotrków

110 kV line Grudziądz –Wąbrzeźno

Total work time on line connected with insulation replacement (hours) – electric power supply system hazard

528

432

Number of 15/0, 4 kV disconnected transformer stations and powered by MV, crossing 110 kV line

Installed power of transformers 15/0, 4 kV (MVA) powered by 15 kV, crossing 110 kV lines

2,93

6,7

Disconnection time of particular transformer stations 15/0,4 kV for 110 kV line operations (hours)

Undelivered power resulting from disconnection of 15/0,4 kV (MWh) transformer stations

11,7

14,2

Undelivered electric power resulting from disconnection of LV lines, crossing 110/ kV (MWh) lines

1,1

Total power undelivered to consumers resulting from disconnection of MV and LV (MWh) lines

12,8

Power system loss due to growing load on neighbouring 110 kV (MWh) lines

266,8

216

Costs related to power emergency services for disconnecting MV, LV, earthing lines and admitting the service team for operation (PLN)

56 000

90 000

15,2

PPN - live conductor operations on 400 kv, 220 kv and 110 kv overhead transmission and distribution lines in ENERGA-OPERATOR S.A., Toruń Branch

PPN operations on 400 kV, 220 kV and 110 kV overhead transmission lines mean: • operation of electric power supply systems without hazard, • reduction of power loss in the transmission and distribution system, • no disconnecting of crossing 220 kV, 110 kV, MV and LV lines, • no restrictions in electric power sales from extra high voltage, HV, MV and LV systems, • reduction of power system operational costs, • improving Occupational Safety and Hygiene in operational and repair jobs, • developing proper habits in operational and repair jobs, • increasing the operational level, • reduction of time required for the operation, • more environmental friendly way.

BIBLIOGRAFIA 1. Michniewski R., Aspekty techniczne i ekonomiczne prowadzenia prac pod napięciem w ZE Toruń SA, Energetyka, 2002, nr 10/11. 2. Michniewski R., Czy warto wykonywać PPN na liniach przesyłowych w Polsce?, Energetyka, 2006, nr 6 i Biuletyn Informacyjny PTPiREE, 2006, nr 4. 3. Michniewski R., Prace pod napięciem na słupach odporowych i odporowo-narożnych linii 400 kV – uzyskiwane efekty ekonomiczne, IX Konferencja „Prace pod napięciem w sieciach nn, SN i WN w Polsce i na świecie”, Gdańsk 21–22.06.2007. 4. Michniewski R., Prace pod napięciem na słupach odporowych i odporowo-narożnych linii 400kV – efekty ekonomiczne, Biuletyn Branżowy, 2007, nr 8, Energia elektryczna, PTPiREE. 5. Krawulski A., Niejadlik T., Prace pod napięciem na liniach 400 kV i 220 kV wykonywane w Koncernie ENERGA SA Oddział w Toruniu, VIII Międzynarodowa Konferencja ICOLIM 2006, Czechy, Praga, 7–9.06.2006. 6. Michniewski R., Prace pod napięciem realizowane przez ENERGA-OPERATOR SA Oddział w Toruniu na sieci przesyłowej 400 kV, 220 kV i 110 kV – uzyskane efekty ekonomiczne i związane z ochroną środowiska, IX Międzynarodowa Konferencja ICOLIM 2008 Polska, Toruń, 4–6.06.2008. 7. Dmoch K., Konieczny Z., Prace pod napięciem w ENERGA-OPERATOR SA – nowe technologie na liniach napowietrznych WN, IX Międzynarodowa Konferencja ICOLIM 2008 Polska, Toruń, 4–6.06.2008. 8. Michniewski R., Michniewski D., Niejadlik T., Wykonywanie prac pod napięciem w Polsce na napowietrznych liniach 110 kV, VII Międzynarodowa Konferencja ICOLIM 2004, Rumunia, Bukareszt, 25–27.05.2004.

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Author / Biographie

Sławomir Noske Elbląg / Polska Head of the ENERGA-OPERATOR S.A. Elbląg Branch Technical Department in the Elbląg Electricity Distribution Region. Employed by the company since 1991. Graduate of the Poznań University of Technology Faculty of Electrical Engineering. Also completed postgraduate law and management studies at the Gdansk University of Technology as well as MBA studies at the Gdansk Foundation for Management Development. In 2006 began writing doctoral thesis on: ‘Diagnosis of medium voltage power lines using the self-extinguishing voltage wave method of measuring partial discharges.’ (Diagnostyka linii kablowych średniego napięcia z wykorzystaniem badania wyładowań niezupełnych metodą samogasnącej fali napięciowej.) Since 1995 has been working in a team for implementing a computer system to support the operation of electricity networks, and is currently in charge of the implementation and further development of this system. Since 2004 is in charge of work concerning the diagnosis of MV cables on the basis of partial discharge measurements – using the Seba OWTS-25 system – and is a participant of a Poznań University of Technology Faculty of Electrical Engineering research project.

Measurement of partial discharges in medium voltage cable lines

MEASUREMENT OF PARTIAL DISCHARGES IN MEDIUM VOLTAGE CABLE LINES Sławomir Noske / ENERGA-OPERATOR S.A. Elbląg Branch

PARTIAL DISCHARGES A partial discharge is limited in space to an electrical discharge that partially bridges an insulator. It is caused by a localised concentration of voltage within an insulator or on its surface. When the local electric field exceeds the value of inception voltage, a first seed electron starts an electron avalanche. Fig. 1 shows an equivalent circuit with a void where a partial discharge occurs. Partial discharges vary, depending on a number of factors which include the type of insulation as well as the location and geometry of the voids.

Cb Cc

Fig. 1. Equivalent circuit diagram of cable line with a void in the insulation where capacities Cc, Cb represent insulation located serial and parallel to the void.

The probability of discharges occurring may, among other things, depend on the type insulation. Partial discharges may result from the insulation’s deteriorating state. Likewise, the degradation of insulation quality may result from the partial discharges, i.e. insulation material degradation and partial discharges mutually affect one another. On account of the fact that partial discharges occur in association with the deteriorating state of the insulation, they are harmful and through repeated occurrences frequently lead to power failure. They damage insulation when, for example, high energy electrons break chemical bonds in the polymers or through the aggressive effects of chemical decay resulting from the break up of molecules.

Abstract Medium voltage cable lines are an important element of electricity distribution company property. They are used to supply electricity to highly urbanised areas, where users are particularly sensitive to power failures and the consequences are very expensive to remedy. The management of such networks has so far chiefly relied on the analysis of failure frequency. Increasing failure frequency has been regarded as the deciding factor in assessing a given power cable line’s technical condition. Now developments in measuring apparatus allow for new ways of examining the exploitation of power networks, providing a greater understanding of their technical state. Thanks to the new information, it is now possible to improve the operation and management of cable networks. One can now examine the technical condition of the insula-

tion of various elements within a power cable line. One of these modern methods involves the measurement of partial discharges.

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Rozwój informatyczny i technologiczny w ostatnich dekadach XX wieku pozwolił na budowę przewoźnych urządzeńDISCHARGES dających możliwość pomiaru wyładowań niezupełnych w eksploatowanych MEASUREMENT OF PARTIAL Partial discharges were recognised as harmful to insulation already at the start of the 20th century, when sieciach energetycznych. high voltage devices started being used. The first industrial tests of partial discharges were carried out in 1940. Developments in technology and computer science the last decades of the 20th(wnz) century the Jednym z rozwiązań pozwalających mierzyćinwyładowania niezupełne w allowed liniach for kablowych construction of devices able to measure partial discharges in active power distribution networks. napięcia jest for system pomiarowy of OWTS-25 firmy SEBA OWTS obecnie Oneśredniego of the solutions allowing the measurement partial discharges (PD) inKMT. medium voltagejest cables is the Seba KMT OWTS-25 system. OWTS is currently used bySA theOddział Elbląg branch of ENERGA-OPERATOR S.A. wykorzystywany przez ENERGA-OPERATOR w Elblągu.

Rys. 2. Wóz pomiarowy z zainstalowanym systemem OWTS-25 Photo. 1. Cable test van using the OWTS-25 system

System ten wykorzystuje jako napięcie probiercze samogasnacą falę napięciową. Wytwarzana jest ona poprzez ładowanie badanego kabla do pożądanego napięcia, a następnie rozładowanie go

This system uses as the test voltage a self-extinguishing voltage wave. It is produced by raising the tested cable voltage przez to a required levelzaprojektowaną and then discharging through an air-core coil. The voltage frequency specjalnie cewkęit bezrdzeniową. Częstotliwość napięcia zależnadejest od pends on the cable’s capacitance and the coil’s inductance. In tested cables this frequency is generally within W praktyce, dla badanych liniilosses kablowych mieści się pojemności kabla i indukcyjności cewki. the range of 200–800 Hz. Suppression of the voltage amplitude is associated with dielectric in the tested cable. ona w granicach 200–800 Hz. Tłumienie zanikającej amplitudy napięcia związane jest ze

stratami dielektrycznymi w badanym kablu. 1 f  2π LC

OWTS mierzy falę napięciową powstałą od ładunku indukowanego podczas wyładowania

OWTS measures the voltage wave from the load induced during the partial discharge. It spreads in two niezupełnego. napięciowa rozchodzi sięheading w dwóch Aparatura mierzy falęvoltage biegnącą w opposite directions. The Fala device first measures the wave forkierunkach. the cable end connected to it (the wave proportional the load produced during the PD) napięciowa and next the proporcjonalna other wave after do it has rebounded kierunku tokońca z value podłączoną aparaturą (fala wartości ładunku from the other end of the cable. Measurement of the time difference between the two waves allows us to locate powstałego podczas wnz), a następnie odbitącalibration od drugiego końca kabla.toPomiar exactly where the partial discharge occurred (Fig. 3).falę Pre-test allows the device measureróżnicy PD loadczasu intensity in picoCoulombs (pC). This calibration is conducted in accordance with norm IEC 60270.

między pomierzonymi falami pozwala określić miejsce wystąpienia wyładowania niezupełnego (rys.

3). Dokonana przed pomiarem kalibracja pozwala na wyskalowanie aparatury i pomiar

intensywności wyładowania wnz w pikokulombach (pC). Kalibracja dokonywana jest zgodnie z PNEN 60270 (tłumaczenie międzynarodowej normy IEC 60270). Measurement of partial discharges in medium voltage cable lines

q/2

l -x

q/2





q/2



l 



l -x

Detekcja  wnz



Detekcja wnz



Fig. 2. Diagram of wave propagation resulting from a partial discharge

Rys. 3. Schematyczny obraz rozchodzenia się fali powstałej w wyniku wyładowania niezupełnego

t1  t2 

x v

l  x

Δt t 2  t1

x

l  v Δt 2

Analiza i diagnoza wyładowań niezupełnych ANALYSIS AND DIAGNOSIS OF PARTIAL DISCHARGES Analysis of OWTS test results provides information on the discharge distribution along the cable. The Analiza wyników basic information includes: pomiaru dokonanych systemem OWTS dostarcza informacji o rozkładzie • The partial discharge inception voltage wyładowań w funkcji długości kabla. Do podstawowych informacji uzyskanych z analizy • The maximal and medium value of the apparent charge with the incipient voltage of partial discharges. należą: ‘The PD impulse apparent charge is the load that when injected very briefly between the terminals of a testing causes the same reading on the measuring device as the actual PD impulse. The apparent  device Napięcie początkowe wyładowań niezupełnych charge is expressed in picocoulombs (pC) [3]  Wartość średniavalue i maksymalna ładunku pozornego przy • The maximal and medium of the apparent charge with a Uo value testnapięciu voltage początkowym • PD occurrence frequency with a Uo value test voltage wyładowań niezupełnych. „Ładunek pozorny impulsu wnz odpowiada ładunkowi, • The maximal and medium value of the apparent charge with a test voltage between Uo and 2Uo który frequency wstrzyknięty w bardzo między zaciski obiektu badanego • PD occurrence with a test voltagekrótkim between czasie Uo and 2Uo • Graphs linearly mapping the distribution of discharges throughout the entire cable (Fig. 4) • Anomalies in the number and level of PDs with a test voltage up to Uo or between V0 and 2Uo. This parameter is not automatically defined in the test analysis process but by the person analysing the test results on the basis of obtained graphs linearly mapping discharge distribution along the entire cable. Increased PD occurrence in a given fragment of a cable section that clearly stands out from the level of PD activity in the rest of that section is considered an anomaly. In such cases the analyst defines the maximal value of the partial discharges and the location where they occur.

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Fig. 3. An example of measurement results. Partial discharges are approximately located between the 210th m and 230th m of the cable (the distribution of discharges along the entire cable are divided into each phase – every point represents a single PD and the discharge value is given in pC).

Acquiring analysis results using the length function allows us to view the cable as it really is, i.e. as a line. This is a new quality in conducting cable tests Analysis of PD measurement results provides a unique collection of data. By interpreting this data, one can carry out a diagnosis concerning the technical condition of specific elements within a power line.

PARTIAL DISCHARGES IN PILC CABLES At the ENERGA-OPERTOR S.A. Elbląg Branch PILC cables account for c. 65% of its MV cables. Currently no new PILC lines are constructed as they are being replaced by XLPE cables. Thus the purpose of PD diagnosis in PILC cables is to assess the technical condition of the insulation and track the ageing process. Partial discharges in PILC cables vary in number and value over time. This phenomenon may be observed thanks to on-line PD measurements of medium voltage networks. Fig. 4 is an example of a 3D diagram using cable length and time functions to display PD measurements taken in Holland.

Fig. 4. 3D diagram presenting partial discharge distribution in the length function of an on-line measurement taken over a period of 8 days (with a clear discharge level change in the time function)

Measurement of partial discharges in medium voltage cable lines

Fig. 5. Change in the level of partial discharges depending on the load level in the cable

20,00

18,00

16,00

14,00

12,00

10,00

l [km]

[km]

Figure 5 shows the dependence between the load in the cable and the value of partial discharges. The PD level rises when the load (pressure and temperature in the cable) falls. When diagnosing the technical condition of PILC lines on the basis of partial discharge measurements, one needs to take into account that: • Partial discharges may occur in the cable insulation, but their appearance is most usually of a dispersed nature • The level of discharges and their intensity varies in time and is dependent on the level to which the cable is loaded. This considerably hinders tracing changes associated with the deteriorating state of insulation. • Practical experience has shown that the level of discharges is dependent on the quality of the cable. In the past a country’s economic condition was undoubtedly a factor determining the quality of cables. Therefore older cables are not always characterised by a higher level of PDs (the ageing structure of a PILC cable line is shown in Fig. 6). The example of a line comprising two cable sections from different years (with different PD levels and intensities) is presented in Fig. 7.

10,00

8,00

6,00

4,00

2,00

2,00 0,00

19 52 19 58 1919 6 52 1 1 19 9 63 1690 19 65 1693 67 191 6966 9 1919 6971 1 19 9 73 7 192 19 75 1795 77 191 7987 9 1919 8181 1 19 9 8 8 3 194 19 85 1897 87 191 9908 9 1919 9391 1 19 9 9 9 3 196 19 95 1999 9 201 7 0929 9 2020 0501 2 20 0 0 0 3 208 05 20 07 20 09

0,00

długość kabli PILC

Fig. 6 The length of PILC cables installed in the MV network in specific years by ENERGA-Operator SA Elbląg Branch.

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Fig. 7. Cable line comprising two cable sections (A – HAKnFtA 3x120 mm2, built in 1979; B – HAKnFtA 3x120 mm2, built in 1984). Section A – breakdown voltage below V0, discharge values up to 8,000 pC, voltage up to 1.7V0 only with individual discharges of c. 25,000 pC. Section B – no discharges with V0 voltage, the discharge level exceeds 100,000 pC with test voltage values up to 1.7V0.

The above mentioned phenomena mean that diagnosing the state of insulation in these cables is difficult and requires a lot of experience. The current state of research has not yet allowed us to determine a standard PD level beyond which the operator should decide to change an entire section in a cable network. In assessing the technical condition of cables one should pay particular attention to anomalies. In this case anomalies are places where there is an increased level of PDs. Despite the lack of hard and fast rules to determine the assessment of PILC insulation, there are methods of facilitating decisions concerning operation. Below is an example of a cable line whose section, on the basis of PD tests carried out after a power failure, is changed. In this case it was decided that in order to prevent further power failures the application of a cable repair joint would be inadequate.

Example 1 Fig 8 shows cable line HAKnFtA 3x120 mm2, its route map and the results of its PD analysis. With a V0 voltage, two places on the cable appear to have increased PD levels (30–50 m and 280–300 m).

Fig. 8. The distribution of partial discharges on the examined cable line before the power failure.

Measurement of partial discharges in medium voltage cable lines

The line was damaged at approximately metre 290. On the basis of acquired data, it was decided that that the whole cable section from the 260 metre cable box to the substation terminal needed to be changed. The repairs were not limited to the application of a cable joint. The results of a PD test carried out after the repair are presented in Fig. 9. They show that there were no discharges in the repaired section and thus potential areas of subsequent power failure were removed.

Fig. 9. The distribution of partial discharges after the removal of the faulty cable section (marked red)

PARTIAL DISCHARGES IN XLPE CABLES The insulation of XLPE cables should be free of partial discharges. Any discharges would suggest faults in the cable itself or the fittings. The hysteresis curve of the ignition and extinction of PDs in such cables shows that discharges may be dangerous if their voltage is higher than the working voltage. If a partial discharges ignite with a voltage higher than the rated voltage (e.g. when there is overvoltage in the network) they have to extinguish once working voltage is returned (i.e. the extinction voltage is lower than the ignition voltage). One should bear in mind that PD measurements may not identify all insulation faults, which may also be caused by water treeing. This phenomenon is particularly observable in lines using non-cross-linked polyethylene insulation. The presence of moisture speeds up the insulation’s ageing process and thus damages the cable. Despite these difficulties, PD measurements do provide new opportunities in acquiring fuller knowledge of the technical condition of this type of cable line. Presented below is an example of PD measurements identifying an incorrectly installed cable joint. Such a fault cannot be detected by any other measuring method. Example 2 A 515 m line using a XRUHAKXS 120 mm2 cable and comprising two sections (360 m and 155 m) that were connected by POLJ-24 type cable joints installed by RAYCHEM and with POLT-24 type terminals also installed by that company. Before the line became operational voltage test and leak test measurements were carried out, which showed everything to be in good working order. Bearing in mind that the cable installation process was fully supervised by the regional electricity distribution services and that the fittings were mounted by trained and highly experienced personnel, one could confidently assume that the line was indeed free of any faults. Nevertheless, a PD test proved that a fault in fact existed: there was an increased level of discharges at the 360th metre in the L3 phase (Fig. 10).

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Sławomir Noske / ENERGA-OPERATOR S.A. Elbląg Branch

112

Fig. 10. The distribution of partial discharges in the 360 m joint (L3 phase) with a test voltage value up to V0 and also up to 2Uo

Partial discharges occurred in a place where two cable sections were joined. This indicated a joint fault in the L3 phase. Partial discharges occur with V0 voltage and this causes the danger of power failure. On the basis of explanations provided by the manufacturers of the cable joint the most probable reason for the fault was established: the fitters had failed to apply a heat shrink cover on one of the connectors. The line was built in 2005 and for three years it was subjected to regular tests which revealed no changes (rise) in the level of discharges; the line appeared to be undamaged. In this case one may assume that insulation degradation proceeded very slowly. In order to confirm the PD testing results, the faulty joint was cut out and examined in a Poznań University of Technology laboratory, using James G. Biddle Co. equipment. The test findings verified those obtained from the OWTS equipment. 16000 16000

14000

12000

2005-06-01

10000 10000

2005-09-26 2006-10-02

8000 8000 6000 6000

2005-06-01 2005-09-26 2006-10-02

2007-01-25

2007-09-12

2008-02-12

4000

2000

0 PD-Uośr

PD-Uo avg

PD-Uomax

PD-Uo max

PD-2Uośr

PD-2Uo avg

PD-2Uomax

Fig. 11. Comparison of PD measurement test results, values given in pC

PD-2Uo max

In the laboratory registered discharges with a value of several score pC (whereas in situ measurements registered discharges with a value of several hundred pC). With such values the initial voltage turned out to be considerably lower than V0 (4 kV).

Photo. 2. Partial discharge image during tests carried out on the faulty cable joint using James G. Biddle Co. apparatus.

Measurement of partial discharges in medium voltage cable lines

Fig. 12. Revealed fault in cable coupling: a heat shrink cover had not been applied.

EXPECTED IMPROVEMENTS IN THE MANAGEMENT OF MV CABLE LINES The introduction of partial discharge diagnostics as a supplement to the testing of MV cables should also involve a change in the management of MV lines. It is important that in appraising the technical condition of a network other information acquired while it is operating is used (see Fig. 13). PD Diagnostics

Faliure Analisis

Technical Parameters

MV cable network mamagement

Cost (ERP system)

Development Plan

Network System

Fig. 13. Model of the integration of data (information technology systems) for the purpose of gathering comprehensive knowledge regarding cable networks.

A new power cable network management system will allow for a reduction of costs in maintaining this significant part of company property by: • Lowering operational costs as a result of a reduced number of power failures. The ability to take preventive measures (replace sections with defective insulation before power failures occur) through observation of the ageing of particular network elements. • Raising the quality of new cable lines. The PD measurement method allows for the location of previously unidentifiable mistakes made in the production and fitting of cable lines (thus replacing faulty elements before a power cable line is made operational). Awareness of greater possibilities of monitoring installation work also naturally raises its quality. • Reducing investment and repair costs through a proper prioritising of maintenance procedures (it is not always necessary to change a whole cable section when the replacement of some faulty elements will do), as well as deferring such costs thanks to a better knowledge of the actual state of cable line element insulations (by observing the cable line ageing process). Application of the above measures will ensure medium voltage cable networks of greater reliability and thus increase user satisfaction. By reducing the number of power failures, the quality of customer service will be improved and consequently meet standards set not only by law but also by company policy.

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Sławomir Noske / ENERGA-OPERATOR S.A. Elbląg Branch

LITERATURE 1. Gulski E., Diagnozowanie wyładowań niezupełnych w urządzeniach wysokiego napięcia w eksploatacji, Warszawa, Oficyna Wydawnicza Politechniki Warszawskiej, 2003. 2. Guide for partial discharge measurements in compliance to IEC 60270, CIGRE Working Group D1.33, 2008. 3. Noske S., Efektywne zarządzanie siecią kablową SN, Elektro-info, 2009, nr 1–2. 4. Noske S., Wykorzystanie diagnostyki opartej o pomiar wyładowań niezupełnych do zarządzania siecią kablową średniego napięcia, Konferencyjne Infotech 2008. 5. PN-EN 60270, Wysokonapięciowa technika probiercza. Pomiar wyładowań niezupełnych, PKN, Warszawa 2003. 6. Rakowska A., Kryteria oceny weryfikujące jakość polietylenu usieciowanego stosowanego jako izolacja kabli elektroenergetycznych, Poznań, Wydawnictwo Politechniki Poznańskiej, 2000. 7. Rakowska A., Siodła K., Noske S., Wyniki badań wyładowań niezupełnych jako źródło informacji wspomagających zarządzanie siecią kablową średnich napięć, Przegląd Elektrotechniczny, 2008, nr 10. 8. Van der Wielen P., Steennis F.: First Field Experience of On-line Partial Discharge Monitoring of MV Cable Systems with Location, 20th International Conference on Electricity Distribution, Prague 2009. 9. Wester F., Condition Assessment of Power Cables using Partial Discharge Diagnosis at Damped AC Voltages, Optima Grafische Communicatie, Rotterdam 2004.

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