September 23 - 29, 2013
UTILITY PRACTICE & EXPERIENCE
Turkish Transmission Utility Looks to Silicone Insulators to Reduce Construction & Maintenance Costs Strategically located at the crossroads of three continents, Turkey has for centuries stood as a meeting point between Asia and Europe, between east and west. With a mostly young and growing population, rapid urbanization and until recently strong economic growth, this emerging country now faces numerous challenges to meet its future energy needs. Electricity consumption, for example, is increasing by an average of 8 to 9% a year, and significant investments will be needed in generation, transmission and distribution to balance power system supply with this spiraling demand.
to as low as -43 °C in eastern Anatolia. Moreover, typical daily fluctuations can be as high as 20°C, making it seem that all four seasons can be experienced on the same day. Few other countries face such dramatic climatic variations in service conditions for the power grid.
Helping the country to satisfy future generation needs are some positive climatic factors. For one, there is high potential for wind energy along the western coast while an average of 7.2 hours of sunshine each day means an abundance of solar energy. Moreover, with plentiful rain and generous water resources, there seem ample available sources of renewable energy. But Turkey’s geography also poses certain problems for its power system. The country is surrounded by vast bodies of water: the Black Sea to the north, the Marmara and Aegean on the west and the Mediterranean to the south – in all cases with long coastlines. Each has its own specific character in terms of salinity, with salt concentrations that can vary from relatively low in the Black Sea (e.g. 18 parts per thousand) to more than double that level in the Mediterranean. As the natural bridge between Asia, Africa and Europe, Turkey also seems to have inherited several distinct climatic regions from each. With an average monthly relative humidity of 80% and annual precipitation of up to 1400 mm, daily temperatures can range from a sweltering +45°C in southeastern Anatolia
Turkey’s Power Sector
The Turkish electricity market has undergone significant structural change over the past 15 years. As a first step towards an open, competitive market, the former stateowned utility (TEAŞ) was divided up into three successor organizations: the Electricity Generation Company (EUAŞ), the Turkish Electricity Transmission Company (TEIAŞ) and
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INMR Contributor and T&D specialist Raouf Znaidi visits the Turkish Electricity Transmission Company to report on future plans for expansion as well as how this challenging environment is affecting selection and maintenance of critical components such as insulators for lines and substations.
the Turkish Electricity Trading and Contracting Company (TETAŞ). In addition, an entirely new entity – the Energy Market Regulatory Authority or EMRA – was established to oversee all energy market activities. Any prospective investor in this sector must apply to EMRA to obtain the license required to develop and operate an energy facility.
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As a second step, liberalization of the electricity market through privatizing distribution and generation assets has brought several local and international companies into the Turkish energy sector. One of the most important of these, Enerjisa, was awarded the first privatization license and is also among the local companies most involved in developing hydraulic and wind power generation.
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lines in accordance with all TEIAŞ technical specifications but also with a view to optimizing costs, which we estimate at about US$ 190,000/km and US$ 250,000/km for 154 kV & 380 kV respectively.” Ayranci adds that, apart form its role in line construction, Enerjisa is also involved in alternative power generation, particularly thermal and wind. Future plans in this regard are to expand the large natural gas-fired plant in Bandirma as well as two wind power plants in Mersin and Balikesir. This, he notes, will represent the second phase of the company’s capital investment plan aimed at developing at least 5000 MW of new generation capacity by 2015.
Silicone insulators recently installed at Turkish substation.
According to Enerjisa’s Directorate Project Manager, Mustafa Ayranci, total installed power in Turkey as of August 2011 stood at approximately 55,000 megawatts, produced predominately from thermal plants but also increasingly from hydroelectric, geothermal and wind power. Enerjisa Generation, for example, is targeting a minimum installed power of 5000 MW by 2015, with the large majority based on renewables. Ayranci goes on to indicate that wind power offers perhaps the greatest opportunity for future development and that, with an estimated total of 48 GW of
onshore and offshore, Turkey exceeds the wind power potential of most European countries. Nafiz Ozcan, the company’s expert in overhead transmission, points out that all this power is transferred to TEIAŞ as the main customer, using existing and newly built lines. In certain cases, based on mutual agreement, new lines have been constructed entirely by Enerjisa but under a Ayranci. Enerjisa involved in both power supervised contract for TEIAŞ. generation and distribution. Says Ozcan “basically, we built these new high performing transmission
Fig 1: Installed power in Turkey by energy source (2010).
Photos: INMR ©
Glass strings have traditionally been the dominant type of insulator used on Turkish transmission lines.
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“Since many of our lines do not suffer from pollution, turning progressively to silicone-housed insulators for these during the past three years has been based mainly on other factors, particularly their attractive acquisition cost.”
improving existing transmission infrastructure so as to assure a more consistent high quality of service. This goal has become ever more important since TEIAŞ expects electricity demand to grow by about 7.5% annually over the course of its 2012-2018 Plan.
Photos: INMR ©
New investment program by TEIAŞ aims to improve reliability with optimized costs.
Turkish Electricity Transmission Corp. (TEIAŞ):
Ozcan. Transmission lines built according to TEIAŞ technical specifications. with more than the equivalent of US$ 320,000,000 allocated to expanding our transmission system. At the same time, we are aiming to optimize these investment costs as much as possible.”
In contrast to the role of private companies such as Enerjisa, the Turkish Electricity Transmission Corp. (TEIAŞ) is the sole owner of the HV Yildir goes on to point out that and EHV network and also responsible resources will also be devoted to for planning, construction, operation and maintenance of this system. TEIAŞ also prepares a Transmission System Investment Plan as well as a 10-Year Statement Report for development of the country’s transmission capabilities.
Among the key projects when it comes to expansion of the grid will be future dual interconnections of Turkey’s national electricity system to the European system to the North and to a group of countries to the south, including Egypt, Jordan, Libya and Lebanon among others. Glass has traditionally been the dominant insulator technology specified on the Turkish overhead transmission network with some use of porcelain on lines but more
TEIAŞ General Manager, Kemal Yildir, explains that one of the principal goals of the investment program in 2012 will be to renew and further develop the country’s electrical infrastructure. “As during the past year,” he says, “significant new projects will be undertaken, Kemal Yildir (center) reviews TEIAŞ investment program with INMR’s Raouf Znaidi (right).
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Transmission lines near Istanbul suffer from high humidity combined with marine and industrial pollution, with additional vandalism problems that lead to shattered glass discs.
frequently at substations. Up until recent years, composite insulators have played little to no role. But now that seems about to change. While a CIGRE study on experience with composite insulators found that superior pollution performance was the main reason utilities decide to use them, this has apparently not been the sole consideration at TEIAŞ. Says Yildir, “many of our lines where we are now installing composite insulators do not suffer from pollution. Our turning progressively to siliconehoused insulators in these cases has therefore been based on other factors, especially their increasingly attractive acquisition cost. In addition, we feel that such insulators offer us further potential for savings when it comes to installation and maintenance costs compared against conventional insulator technologies.”
Table 1: TEIAŞ Transmission System (Aug 2011) Voltage
380 kV
220 kV
154 kV
66 kV
Total
Substations
Circuit Km
16,000
85
35,000
510
51,595
588
Table 2: Number of Outages on TEIAŞ Transmission Lines (by end of 2010) Voltage (kV)
Length of System
Total Number of Outages
Period of Availability(days)
Outage Rates/100km
380
16,000
1264
345.95
8.36
154
35,000
3051
352.38
8.80
66
510
89
365
13.32
Total
51,595
4404
354.45
8.63
Yildir also observes that there seems to be a growing cost efficiency when it comes to the production and application of the latest generation of silicone composite insulators, meaning there may be even further cost savings to be realized in the future.
Turkish Transmission System
As of August 2011, the TEIAŞ network comprised some 51,600 circuit-km of overhead lines operating at 380 kV, 220 kV, 154 kV & 66 kV.
Photo: INMR ©
Since part of this network is exposed to vast open sea, insulation often has to be designed to resist continuous exposure to marine and in some cases industrial pollution as well. There are also high levels of ultraviolet radiation as well as frequent large daily temperature fluctuations. For example, with the Sea of Marmara in the country’s northwest, some HV lines near the commercial hub of Istanbul are especially vulnerable.
380 kV tower near Ankara employs 24 standard profile glass discs in tension and 22 in suspension.
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According to Transmission Maintenance Manager Hikmet Ozdemir, TEIAŞ experienced a total of some 4400 transmission outages during 2010, with an overall outage rate for the entire system of 8.63
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Trial application of RTV silicone coatings in Turkey increased initial insulator costs at substations by about 60%, but has greatly improved performance under polluted conditions.
Golbasi Substation is an example of a location where composite insulator technology is being progressively applied to reduce costs. per 100 km. Ozdemir says that new maintenance policies are now being developed with the objective of reducing this rate. Table 2, provides an overview of outages recorded at each transmission voltage and highlight the problems affecting the country’s old 66 kV network. According to Ozdemir, major 154 kV and 380 kV lines near the capital city of Ankara and the surrounding area are generally insulated with 10 or 11 and 22 to 24 standard profile glass discs respectively. These, he says, have typically not experienced any serious operating problems. By contrast, lines in other parts of the country suffer from high humidity combined with marine and industrial pollution. Vandalism problems affecting glass discs have also been reported. For example, the 380 kV HabiplerZekeriyaköy line west of Istanbul has had a history of extensive problems related to pollution flashover and vandalism and experienced up to 3 outages per day, increasing outage rate in the Istanbul area to 11.43 per 100 km. This was one of the lines
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where TEIAŞ finally decided to turn to composite insulators to deal with these problematic service conditions. Ozdemir points out that the benefits of this move have extended beyond overcoming pollution and also included important economic gains. Explains Ozdemir, “the insulators we selected to replace existing glass anti-fog disc insulators, were siliconehoused alternating shed designs that allowed us to effectively deal with the pollution problem. At the same time, the acquisition cost of these new insulators was less than half that of the equivalent glass cap & pin string – and this does not even factor in the savings related to their being mostly maintenance free.” Indeed, reducing maintenance requirements at substations as well as on lines has been one of the key goals at TEIAŞ. In this regard, alternatives have been looked at to replace the costly frequent washing of porcelain at stations in industrial areas such as the North. As first step in this direction, 4 years ago trials were begun with RTV silicone coatings applied to substation porcelain by an outside contractor. While this increased initial insulator cost by about 60%, these coated insulators are still
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Ozdemir. Some TEIAS lines suffer heavily from pollution flashover as well as vandalism.
performing reliably and Ozdemir reports that maintenance staff are very satisfied with how this technology has improved substation insulation performance under pollution. The Golbasi Substation, however, provides a good example that composite line insulators are being installed in Turkey even when pollution is not the dominant concern. Located in a rocky, agricultural area just outside Ankara, there is little visual evidence of pollutants accumulating on insulator surfaces in spite of noise from surface discharge activity clearly evident, even on a sunny afternoon. Mustafa Danaci, who has worked at the substation for more than three decades, explains that noise level here is more or less constant
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Porcelain housings at Golbasi substation.
280 mm to 430 mm respectively. Alternatively, there is some use of porcelain long rods as well and these are usually designed with from 900 mm to 1200 mm of creepage. In the case of Ankara, cap & pin strings account for about 70 percent of all insulators now in service on regional distribution lines.
throughout the day and night and is probably linked to localized high humidity. The important point, he says, is that he cannot recall any major pollution flashover incidents.
Photos: INMR ©
Turkish Distribution System
Almost all 36 kV lines in Turkey insulated with three suspension or four tension locally produced porcelain cap & pin insulators with cement pole structure.
While the Turkish Electricity Distribution Co. (TEDAS) and its regional affiliates still dominate distribution of electricity across Turkey, this is gradually changing as new players enter the business. In fact, the country’s distribution system has been divided into 21 regions with the goal of privatizing all but one of these. Enerjisa Baskent Distribution Co. is an example of Members of Enerjisa’s engineering team discuss the new private firms resolving high outage rate on distribution system. in this sector and operates and maintains a network of some 27,000 circuit-km of 36 kV, 15 kV & Kalkan and Aydoğan explain that in order to reduce outages a global 6.3 kV lines that supply 6.6 million maintenance scheme will be people across 7 cities, including conducted each year that includes Ankara. a program to wash insulators, particularly on de-energized coastal Traditionally, the large majority of lines. This will contribute to the 36 kV lines in Turkey are insulated with a string of three porcelain cap & goal of reduce pollution flashovers and related power interruptions and pin insulators of standard or anti-fog improve service quality. design and with total creepage of
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As of the end of 2010, Enerjisa Distribution’s system had experienced a total of 5344 outages, corresponding to an annual rate of about 20 per 100 km. According to Engineers Emrah Kalkan and Mustafa Aydoğan, the main cause of this relatively high rate is the ageing distribution system acquired by Enerjisa only two years ago. Other problems affecting line performance have been pollution as well as birdtriggered outages, especially during migration season.
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