Various case studies On operation and control schemes for grid sub-station contd….

Er. P.K.Pattanaik, is presently working with OPTCL as General Manager, EHT (O&M) Circle Bhubaneswar - Odisha and associated with the Protection and Control schemes of Electrical systems. Having 29 years of technical experience on various HT and EHT voltage level in the field of transmission sector. Specialization on the development technoeconomical design of protection control schemes for system development and planning. At present involved with various on-going projects on GIS, SAS and updated Remote SCADA control stations of OPTCL. Published 105 technical papers in National and International arena and is a regular contributor to the National journals like Electrical Mirror, Electrical India, CBIP journal and IEEMA journal and author of many technical books. Also Awarded in various arena on National level. He is also the coordinator of a Nationwide Power Engineers’ Technical Group named “SPARK- Ignited to share” consisting of Senior Electrical Engineers from different parts of the country. ele.pkpattanaik@optcl.co.in

VARIOUS CASE STUDIES VARIOUS CASE STUDIES ON OPERATION AND CONTROL ON OPERATION AND CONTROL SCHEMES FOR GRID SUB-STATION SCHEMES FOR GRID SUB-STATION Contd…. Contd….

case study

1. Introduction: For the last few months, the response of the readers to the case studies on various incidents is overwhelming. Hence this month we are again choosing the write up on similar kind of studies for developing the synchronization of practical observation to the theoretical concepts. The analysis of each incident being supported by actual observations had been described during the situation to add awareness amongst the operation, testing and commissioning engineers to know the cause of problems and be helpful for easy rectification of the problems. This can also help to develop economic schemes for the smooth running of the operation and control system in the Grid Sub-Station. 2.1. Replacement of 400 KV LA: At 400/220/132KV Grid Sub-Station, it was found with objectionable value third harmonic resistive current. So the LA was replaced before causing any failure. Observations 1. On routine checkup, this station is used with condition monitoring of system equipment. 2. For the LA monitoring, LCM and wattloss component measurement was the periodic testing for the system. 3. Hence, on the similar practice, this LA was undergone with LCM (Leakage Current Monitoring) and wattloss measurement with periodic interval. 4. The results were found as follows. Sl No Month Results Trend 3rd Har Res Current in micro ampere Wattloss component in mwatt

1 1st 236.6 4737.98 Both 3rd Har 2 4th 287.3 5623.98 Res Current 3 7th 368.5 8754.31 and Wattloss component 4 11th 501.2 10121.22 value in rising trend. Note: This result was found with only one Stack and other stacks were found with normal value and results within limit

5. Similar pattern of rising trend with 3rd harmonic res current incident was also observed with another stack of another LA. 6. But due to circuit exigency and system requirement, necessary shutdown could not be availed. But this LA busted before replacement. Action Taken: 1. On finding the busting of the other similar trend LA insulator stack, immediately this LA was replaced. 2. Initially it was planned for replacement of the suspected LA stack, but considering the importance of the system disturbance due to the failed LA because of non-replacement, the total stacks were replaced. Recommendations: From this type of observation and experience, it was decided that LA stack should be replaced once the trend goes beyond 250 micro ampere and happens to be in rising trend. 2.2. Multi-Tripping of 132 KV Circuit Breaker: 132 KV Transmission line tripped 3 times before to allow hand trip of the system. Observations: 1. This line was connected between two inter-connected stations with sources at both end. 2. This line was provided with Automatic closure system with DEAD TIME BEING 3 Secs and reclaim time being 25Sec. 3. This line was SC (Single circuit Line) with triangular disposition R, Y and B phase. 4. R phase on one side of the SC line. 5. There was phase to ground fault on R phase. 6. On first instance, it was found with single phase to ground fault for R phase, so the gang operated breaker tripped, but closed after its dead time of 3 secs. 7. Similar incident repeated once again after few sec on the same phase of R phase to ground, but reclosed after its dead time of 3 sec. 8. Similar incident again repeated and reclosed again. 9. But this time, it was decided to hand trip the line from both end before to cause such repeated closure. 10. The patrolling team was asked for physical inspection of the total line. 11. It was suspected regarding the issue of suspension insulator string snapping, resulting with lowering of the conductor to ground and causing arcing due to swing. 12. Moment the conductor coming the arching zone, resulting with tripping of the line and reclosing after 3 sec of dead time. Similar incident for the three instances of tripping and reclose. 13. The patrolling team patrolled the full line, but found with no such insulator snapping or no any conductor lowering cases. 14. But it was reported with the case of dump yard burning and smokes evolution under the R phase conductor part. 15. This dumping yard is of hill shape and waste dump yard vehicles were dumping from top of the hill causing heaping of the wastage down yard. 16. Because of such dumping the clearance to the single side R phase conductor was becoming less. 17. But it was well within the allowable zone of around 6 mtrs. 18. On the day of incident or before, there had been smoke fire on this dumping yard by someone, which was causing with smoke evolution and during time of patrolling also it was with smoke under the line. 19. The fire brigade on request of the municipality team was also on the job for extinguishing of the fire. 20. The Electrical wing on arriving at the site inquired about any sound/incident to the fire brigade gang engaged at site. 21. It was reported regarding some intermittent sound and arching on the line far away from the place of their work extinguish site. 22. So, it was confirmed that the case of tripping was due to smoke evolution and on counselling with the team, the line was kept under shutdown. 23. The Fire brigade was counselled to extinguish the fire under the line at the earliest for revival of the line. 24. The extinguish action completed within two days and then line was energized successfully. Technical Analysis: 1. Practically the dumping yard was of bit big in comparison. 2. On dumping from one side of the hill and lowering down to the bottom was causing clearance nearer to R phase conductor as like shown in figure 2.2 3. On the day or before, when fire resulted with smoke due to burning waste dumping, the bloom of smoke with residues caused the path of ionized path to the voltage to appear for tracking of current. 4. So the Ph-ground fault was resulting with Tripping of the line. 5. After DEAD time of 3 secs, this smoke was not of that dense, for which the auto-reclose function was allowing to reclose of the system.

case study

6. Till to the period of 25sec or above as provided for RECLAIM time, this smoke cluster might not be in sufficient for developing the arcing path. 7. So after the elapse of 25 sec and sufficient accumulation rise of smoke cluster was causing tripping again. 8. Operator on finding such and on consulting the station head hand tripped the line from both stations. 2.3. Case for ZERO megger value of Transmission Line: It was reported by LINE JE ( Junior Engineer) followings while meggering ( taking Insulation resistance) of a long TL Line 1. The IR value was shown as 0 Ohm on R Phase 2. The Y and B Phase value showing 1000 MOhm. Observations: - On receiving the information from the LINE JE, the IR value was measured and found with ZERO on Scale II. So it was decided to check the value on scale –I, that starts from minimum range. This time the pointer also deflects towards ZERO, but after few seconds, the value picks up and shown with value of approximately of 200 MOhm. So it was advised to do the followings while to take IR value of long TL 1. Put TL conductor (Lead) used for meggering on EARTH connection till to start of taking the meggring value. 2. Choose Scale –I (Minimum range starting scale) on the megger. 3. Remove the Earth connected TL lead just before taking the IR value. 4. If motorized, allow the motor to run at least for 1 Minute to overcome the induction effect and time constant of the Transmission line. 5. If Hand operated, then allow to rotate the crank continuously for 1 Minute. 6. After elapse of 1 minute, the required reading may come and record the same. 7. If the value still comes as ZERO then the line might have been in problem. Technical Analysis: In general, Transmission Line being surrounded by other TL result with Induction in the system. So while tagging the IR value this induction effect does not allow the reading to obtain correctly and after continuous rotation, this may overcome and show the reading of the IR value. 2.4. Rectification of Breaker Problem: For the interconnected important 132KV line, it was observed with leakage of SF6 Gas and final lock out of the tripping circuit of the breaker. The concerned maintenance engineer was advised to open the isolator on either side of the breaker on equi-potential concept. Explain the procedure for the emergency operation. Explanation: This feeder was connected as the main incomer to this station from a remote station. On actual incident, SF6 leakage alarm was annunciated in the window before attaining the lock out situation. But due to improper planning and non-availability of SF6 gas in the station, the in-time filling of gas could not be attended. So finally the situation of SF6 LOCK OUT resulted. Procedure suggested: 1. Develop on-line parallel path for this feeder, by closing the Bus-coupler Breaker and its isolators. 2. By doing so, the terminal A and B on either side of 89M isolator of the main feeder bay can be developed with point of equi-potential. Point B gets the potential from point C through the path containing Bus-coupler Breaker and Point A gets its potential through its own breaker path. 3. Now the isolator 89M could be opened without resulting any interruption and problem on the operation. After opening of this isolator 89M the system can be operated through Bus coupler breaker. 4. Then the other side isolator (89L) of the affected breaker could be easily opened for the maintenance shutdown of the affected breaker. Note: Such kind of operation should not be attended with Local condition. Because during the operation of equipotential, if fault would be resulted, then the faulty breaker shall not trip and tripping of Bus coupler breaker shall cause opening of the isolator on load with severe spark and damage to the system. So, Local operation may cause safety to the operator concerned. In practice this operation to be avoided and if so required so emergency then attempt should be made on remote electrical operation only. 2.5. No continuity of CT secondary: At one of the 400/220KV Grid Sub-station, one 220 KV CT of an outgoing feeder was taken shutdown for change of the CT ratio. On checking of the CT secondary, the resistance of the terminals was found OPEN. Actual observation: 1. This line was of DC (Double Circuit) 120 Km, and this feeder was under shutdown with other circuit in service. 2. To avoid induction on the system, Earth switch on both end of the line was closed. 3. The weather was of drizzle type. 4. On observation of CT secondary resistance, it was found with OPEN. 5. This line was in charged condition with this CT.

6. The secondary terminal voltage was checked and found with induction of around 515Volt as measured by Voltmeter. Analysis: 1. As the weather was of drizzle and moist in atmosphere. 2. The other circuit was live with availability of power flow. 3. So the induction on this line was of active in nature. 4. Though the line was earthed at both end, but the induction on the system did not subside and resulted with the flow of ionization current on this line. 5. Hence during measurement of resistance by the multimeter on resistance mode, the value was of indicative as OPEN due to availability of voltage on the terminals. 6. The availability of induction voltage on the secondary circuit of the CT was due to the induction on the primary side of the CT. Recommendation: For working on the secondary side of the HT CT on the long line, earthing must be done at both end of the line with local earthing also to avoid electrocution to the operator. 2.6. Blowing out of PT secondary fuses: At one of the 132/33 KV Grid Sub-station, during the situation of MONKEY fault on 33 KV side, it was observed with blowing out of R and Y phase fuse at the 132 KV PT secondary box. Observations: 1. This station was installed with 3 Nos of 63MVA 132/33 KV Transformers catering the approximate loads of 80MVA to the downstream. 2. One day a MONKEY fault occurred at the 33 KV bus of Station Transformer on B Phase inside the switchyard. 3. Suddenly the concerned feeder was tripped on earth field. 4. After clearance of the fault, the system was availed, but it was found with erratic supply on the secondary side of the 132 KV PT supply. 5. So shutdown was availed and found with blowing out of fuses at PT secondary box on the metering core. 6. On detail checking of the circuit, it was found with the Neutral of both the CORES (Protection and metering) was of single wire. 7. Technically the wires have run from PT Console box to CRP (Control and Relay Panel) as Protection core (E11, E31, E51, E71) and Metering core as (E111, E131, E151 and E71). 8. This was connected with a 7 core cable with E71 being the one wire and common to both Cores. The earthing of the cable was done at Panel end. 9. On checking it was observed with Panel end earthing not connected to Grid Mat. Actions taken: 1. Another 4 core cable was laid for metering core and common neutral wire was taken separately and metering core was ferruled as (E111, E131, E151 and E171). 2. The earthing at Panel end was again connected to EARTH MAT, considering primary and secondary as the same potential. 3. The blown out fuses were replaced by the correct rating fuses and graded with the fuses at panel end. Analysis: 1. Practically the fault has occurred at 33 KV end on B phases So it happens to be reduced voltage on this phase with rise of voltage on the other two healthy phases on the system. 2. Similarly the same has to be reflected on the upper side (132 KV side) of the system. The development of high voltage depends upon the common earthing of the system. 3. In this condition the 132 KV side Primary earthing was not proper, for which healthy R Phase and Y phase might have resulted the rise of voltage. 4. Same time the secondary earthing of PT supply( 110 Volt end) was also not at same potential of the primary. So rise of corresponding voltage causes the blowing out of fuses. Recommendations: It is recommended to provide proper earthing in the system and for the case of PT supply, The star point earthing should be connected to Earth Mat of the Grid Station. EM

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w IE v TER n I

Mr. Deepak Singh Thakur

Business head - india & saarc region, cisBu - mcis DelTa elecTronicS inDia privaTe liMiTeD

Delta is a global innovative provider of switching power supplies and DC brushless fans, as well as a major source for power management solutions, components, visual displays, industrial automation, networking products, and renewable energy solutions. Delta Group has sales offices worldwide and manufacturing plants in Taiwan, China, Thailand, Mexico, India and Europe. As a global innovator in power electronics, Delta's mission is, "To provide innovative, clean and efficient energy solutions for a better tomorrow." Delta is committed to environmental protection and has implemented green, lead-free production and waste management programs for many years.

Q. What are the takeaways of the Delta from the outbreak of the pandemic and how Delta has survived the challenges?

In the last two years of the Covid pandemic we have witnessed relationships of companies- viz-customers being impacted across industries. Lockdowns and drastic curtailing of movement posed the gravest challenges compelling industries to explore innovative ways to engage with their customers. Delta promptly switched to online interactions with key accounts who readily adapted to the new mode of communication realising that it is the only way forward. A perceptible impact on the supply chain, logistics and price hike were other areas of concern. We also learnt lessons on cost saving, how to optimise procurement and plan travel strategy, and the fact that we could still function on reduced budgets i.e., without being expensive we can still deliver. Pruning superfluous expenses, which were conventionally thought to be necessary or indispensable, was another big change.

Q. As the digital interface rapidly increasing, what future holds for the data centres?

Digitization followed by the 5G technology in communication will actually give a huge momentum to digitized business. India is still in 4G stage with a lot of digitization yet to happen, but the moment 5G comes into play most businesses would start adopting far more digitized models. Even as it will majorly impact the existing mega collaborative hyper data centers, 5G would move the market to edge computing, meaning every business will have to store some critical data near to the user or near to their functions. We see ourselves playing a major role in this space.

Q. When it comes to Cloud, how does Delta see itself as a major player?

Cloud is another space that India has potential to grow exponentially. Many hyper-scaler companies are going to invest in India and top players are in some way established in India either directly or through collaborative partner. In fact, in the next 5-6 years we will see a huge boom of data centres where the current installed capacity of 500-600 MW data centres will have add on five times the current capacity each year. There will be projects of more than 300 MW and Delta is already in discussions with some investors. Cloud will have increasing impact on business models such as e-retail shops, banking etc. In fact, top 4-5 collo-players in all the segments including government and private is where Delta has significant presence.

Q. What are the kind of data centres that Delta provides uniquely than other brands?

Delta caters to two kinds of segments, the traditional data centres where infrastructure needs i.e., the UPS, batteries and distribution units, which is the component portion, is provided and the other is engineered-to- order solution where we have skilled architectures in our data centres and have power containers that will be further enhanced with advent of edge computing. Once the edge computing system comes into play then pre-fabricated data centre concept will follow. Delta is gearing up to develop infrastructure to test and manufacture those in India and is in discussions with many customers who are working closely with Delta at the conceptual stage to address their respective demands. Pre-fabricated segment is something that we are already addressing in the smaller edge which is basically of one to six rack data solution centres. Delta is also working on moving from 1 MW pre-fabricated units to multiple MWs.

Q. What is the major factor that gives Delta an edge in the market?

The biggest edge is that Delta is a strongly R&D driven organization with 6-8 percent of its global sales revenue allocated to research and product innovation. We are also the largest ODM and OEM manufacturers of critical components that go into the making of a data centre. Another advantage is our exceptionally competent team that has enriched our knowledge pool, besides the strong service network backup that we have across the country. The biggest strength, however, are our key customers, who are growing in this segment. Presently, we are focused on addressing further demands of our existing customers rather than scouting the market to fetch new clients. We have also deployed a lot of modular architecture with product offerings that are the most compact in the industry that actually allow the customers to grow as the business grows with them, that is much appreciated by our customers. We see ourselves enhancing the modularity and scalability of our pre-fabricated data centres to further enhance our business.

Q. Please give us a brief of Delta’s vision in India?

India is one of the sub regions of Delta, which is a huge focus area that exhibits the global management’s optimism about India as a potential market. The reason why the company is coming up with an R&D centre at Bengaluru for strengthening its capability within India. We are also manufacturing in India that makes it viable to have an R&D facility within India. Delta is seeking to invest more than Rs 500 million in India in terms of new factories such as the upcoming global manufacturing unit in Krishnagarhi on the outskirts of Bengaluru, which once completed will have the capacity to not only cater to a huge captive market in India, but to rest of the world as well. The company also has manufacturing facilities in Rudrapur, Uttarakhand, Bengaluru and Gurugram for different products for each business unit. Intelligence gathering at Delta is done in-house as well as from global initiatives where we work closely with research organizations exploring market trends and studying those reports. Attending various events and workshops also helps and most importantly is the feedback of our customers by engaging closely with them which enables us to align our business accordingly. Manufacturing is also set to boom with ‘Make in India’ of the Indian government giving a boost to our industry. EM

https://deltaelectronicsindia.com/

w IE v TER n I

Mr. ShaileSh MehTa

director MehTa caD caM SySTeMS pvT. lTD

Mehta Cad Cam Systems Private Limited an ISO 9001:2015, Lean Sigma, and CE certificates company is in business since 1989. Constant innovation and progressive investments over years made Mehta Cad Cam one of the largest manufacturer of fiber laser, Co2 laser, CNC, and digital printing machines in India. Quality of products, customer satisfaction and after sales service are the three pillars that makes Mehta Cad Cam Systems a market leader. With our 4 state-of-the-art manufacturing facilities based at Ahmedabad and strong R&D department, we believe in creating machines that solve problems that people in various industries faces.

Q.Our company invest huge amount of money in advance technology in the field of Laser, CNC and Digital Printers. How is Mehta’s business shaping up in India?

As you all know, Mehta Cad Cad Systems has been in business for more than three decades now. We have come so far from being an importer who imports machines and sells them to being India’s leading manufacturer of Fiber Laser, Co2 Laser, CNC, and digital printing machines in India as well as many parts of the world. Our research and development team has developed and is continually working to design machines according to industry specific requirements. Q. Which are the new technological innovation and digital efforts that Mehta Cad Cam is successfully focused on?

As said, new innovation from time to time is the core competency of Mehta Cad Cam Systems, and we always have the intention of developing new applications and new equipment first. Here at Mehta, we always focus on innovation to increase the productivity of production for our clients. We have developed many different laser technologies for marking on various materials of cables. Also, customization for marking on different electrical components like LED bulbs, electrical sockets, MCBs, housings, chargers, etc. at higher and higher speed is always a center of innovation. Q. What are your plans for capacity expansion and for growing your basket of value-added products?

Recently, Mehta is focusing on capacity expansion along with focusing on quality and service and has procured a land area of 40,000 sq. meters to increase the production capacity of the new growing Indian market and satisfy the growing demand for Mehta’s machines worldwide. We have a wide range of product categories; Fiber Laser, Co2 Laser, CNC, Digital Printing Machines, and each product has an equally wide range of applications. Our research and development department is working in each category to develop new and better products to satisfy the needs of more applications.

Q. What are the market’s challenges, particularly in terms of cost, technical advancement, and getting raw materials?

Our major competitors in the line of manufacturing when it comes to the Indian market and the markets outside India are the Chinese manufacturers. At the same time, we are also dependent on China for some of our key components. There are times when it becomes difficult to compete with them in terms of price and we have to compromise on profit. Q.As quality comes with a price, how do you balance quality with affordability?

We at Mehta stand on the principal of providing the best quality to our customers, and we have never had and will never compromise on quality. Rather, we work on our profitability to provide the best at the most affordable price. In order to reduce our dependency on Chinese component manufacturers, we are replacing them with Indian component manufacturers. This will provide us with a more competitive price. Moreover, we are now replacing outsourced components with our own manufactured components. This way, we are able to control quality as well as cost, making our machines more advanced at the most affordable rates. Q.How has Mehta Cad Cam geared up to support the government’s missions?

Of course, our company is focusing on the international market, and our exports are also growing day by day. It definitely helps us as well as our nation to get US dollars, which is one of the major requirement for a 5 trillion-dollar economy like India. We are proud to say that we are a part of the nation's 'Atmanirbhar Bharat Mission’ and are rapidly moving towards making our machines completely indigenously. Q.What are your most advanced solutions to optimize the generation assets?

As stated earlier, we are India’s leading manufacturer of fiber laser marking, cutting, and cleaning machines. We specialize in online marking solutions designed for clear and fast marking on cables and electrical components. We have solution to cut all grades of MS, SS, Al, brass up to 40 mm thick. For complete automation, we also have robotic solutions. We also have fiber laser cleaning solutions.

Q.Which are the most significant projects in India that currently you are working on?

Our product line has many products with applications in various industries. We are working with many government organizations like space and defence organizations like ISRO, DRDO, HAL, etc. for many projects.

Q.What will be the industry's outlook for coming years?

India is becoming a manufacturing hub of the world; this is also generating opportunities for various industries to grow. India, being one of the biggest markets, is now seen as the world's manufacturing hub. The world, including India, is moving towards digitalization and automation. It is a great opportunity for all Indian manufacturers to spread their wings in India and countries across the world and strengthen themselves for future opportunities and challenges. India has the capacity to satisfy the needs of the world market. Those who will capture this opportunity will definitely grow. EM