{"id":53737,"date":"2016-04-09T22:53:26","date_gmt":"2016-04-10T04:53:26","guid":{"rendered":"http:\/\/www.lankaweb.com\/news\/items\/?p=53737"},"modified":"2016-04-09T15:52:46","modified_gmt":"2016-04-09T22:52:46","slug":"power-systems-knowledge-vacuum-in-srilanka","status":"publish","type":"post","link":"https:\/\/www.lankaweb.com\/news\/items\/2016\/04\/09\/power-systems-knowledge-vacuum-in-srilanka\/","title":{"rendered":"POWER SYSTEMS \u2013 KNOWLEDGE VACUUM IN SRILANKA"},"content":{"rendered":"

By Kanthar Balanathan<\/em><\/span><\/h2>\n

DipEE (UK), GradCert (Rel Eng.-Monash), DipBus&Admin (Finance-Massey), CEng. MIEE, MIE (Aust), CPEng (Ret)<\/em><\/p>\n

Former Director and Specialist Power Systems Engineer (Australia)<\/em><\/p>\n

In the month of March 2016, two transformer explosions struck at Biyagama and Kotugoda CEB Grid sub-stations. Media reports state that the German specialists, after investigations revealed the explosion was in the diverter switch, which is the On Load Tap Changer (OLTC). The load throw off (LTO) of the capacity of this Biyagama transformer also cause stability issues and tripped the generators at the Lakvijaya (Norocholai, Puttalam) power plant. Capacity of the generators at Lakvijaya Power Station (LPS) is 3 x 300MW. Transformer at Biyagama is rated for 220\/132\/33kV. Media information state that feeder lines tripped after the transformer caught fire at Biyagama.<\/p>\n

A report by Maheesha Mudugamuwa in the island state that the power station trip was caused by a lightning strike. http:\/\/www.island.lk\/index.php?page_cat=article-details&page=article-details&code_title=141040<\/a>.<\/p>\n

This statement cannot be true. May be the first incident of trip. During the period when this disaster occurred at about 2.15 p.m. there was no lightning or rain. The environment too was normal. \u00a0Indeed, there was no rain at all in the region. Ref: http:\/\/lankaenews.com\/news\/1203\/en<\/a><\/p>\n

Another transformer explosion at Kotugoda caught fire similar to the explosion at the Biyagama Grid Sub-station. Both transformers are similar single phase auto-transformers. It could be a Type Fault<\/em>\u201d on these type of transformers. Type: Takaoka Autotransformer (1983) 132\/\/33kV (secondary), 200\/3, 250\/3, 60\/3 MVA, YNa0d1, ONAN\/ONAF with 13 taps on both. There are three of this type one on each of the phase. Are these transformers made in Germany or Japan?<\/p>\n

    \n
  1. Possible cause: Diverter switch may have contained excessive amount of combustible gases.<\/li>\n
  2. The contacts of the tap changer may have been pitted causing generation of sparks while moving from one tap to the other.<\/li>\n
  3. Oil may have had exceeded levels of moisture.<\/li>\n
  4. Oil condition may have been as sludge, brown oil.<\/li>\n
  5. May be a Type Fault<\/em>\u201d.<\/li>\n
  6. What about the Buchholz relay in the diverter switch. Did it operate to trip?<\/li>\n
  7. What about the Buchholz relay for the Transformer? Did it operate?<\/li>\n
  8. Analysis should be carried out on identifying what relays tripped.<\/li>\n<\/ol>\n

    Root cause of failure therefore, has to be generation of sparks in the diverter switch, subject to excessive level of combustible gases. Primary cause of failure is nothing other than, lack of condition monitoring, and maintenance practice. Speculating about sabotage in the media, is an irresponsible statement, and kind of pass the monkey in a way.<\/p>\n

    Tripping of feeders:<\/p>\n

    It was observed from photographs, smokes were released in high volumes, due to the explosion.<\/p>\n

    It is possible that the smoke clouds, if concentrated under the power lines could ionise and trip on earth fault. Reason being dielectric breakdown of the air as a result of Carbon soots\/ionisation. This could be verified from the operated relays. If E\/F relays has operated on lines then it should be investigated. (Take note, the air was dry and no rainfall at the time of line trip<\/em>)<\/p>\n