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Study on the Damage Pattern Analysis of a 3 Phase 22.9/3.3kV Oil Immersed Transformer and Judgment of the Cause of Its Ignition

3상 22.9/3.3kV 유입변압기의 소손패턴 해석 및 발화원인 판정에 관한 연구

  • 최충석 (전주대학교 소방안전공학과)
  • Received : 2011.04.19
  • Accepted : 2011.05.23
  • Published : 2011.06.01

Abstract

The purpose of this paper is to present the manufacturing defect and damage pattern of a 3 phase 22.9/3.3kV oil immersed transformer, as well as to present an objective basis for the prevention of a similar accident and to secure data for the settlement of PL related disputes. It was found that in order to prevent the occurrence of accidents to transformers, insulating oil analysis, thermal image measurement, and corona discharge diagnosis, etc., were performed by establishing relevant regulation. The result of analysis performed on the external appearance of a transformer to which an accident occurred, the internal insulation resistance and protection system, etc., showed that most of the analysis items were judged to be acceptable. However, it was found that the insulation characteristics between the primary winding and the enclosure, those between the ground and the secondary winding, and those between the primary and secondary windings were inappropriate due to an insulating oil leak caused by damage to the pressure relief valve. From the analysis of the acidity values measured over the past 5 years, it is thought that an increase in carbon dioxide (CO2) caused an increase in the temperature inside the transformer and the increase in the ethylene gas increased the possibility of ignition. Even though 17 years have passed since the transformer was installed, it was found that the system's design, manufacture, maintenance and management have been performed well and the insulating paper was in good condition, and that there was no trace of public access or vandalism. However, in the case of transformers to which accidents have occurred, a melted area between the upper and the intermediate bobbins of the W-phase secondary winding as well as between its intermediate and lower bobbins. It can be seen that a V-pattern was formed at the carbonized area of the transformer and that the depth of the carbonization is deeper at the upper side than the lower side. In addition, it was found that physical bending and deformation occurred inside the secondary winding due to non-uniform pressure while performing transformer winding work. Therefore, since it is obvious that the accident occurred due to a manufacturing defect (winding work defect), it is thought that the manufacturer of the transformer is responsible for the accident and that it is lawful for the manufacture to investigate and prove the concrete cause of the accident according to the Product Liability Law (PLL).

References

  1. W.M. Flanagan, "Handbook of Transformer Design and Applications 2nd Edition", McGraw Hill, Chap.1,8,11, 1992.
  2. 고태언 외 7, "전기기기", pp. 245-368, 2007.
  3. 손제봉 외 4, "전기기기", pp. 104-204, 형설출판사, 2007.
  4. 한국표준협회, "한국산업규격 KS C 4311", 2002.
  5. 한국표준협회, "한국산업규격 KS C 2516", 2002.
  6. 최충석 외 5, "전기화재공학", 도서출판 동화기술, pp. 60, 189-198, 202, 2004.
  7. 최충석 외 2, "과전류에 의해 용단된 소선의 특성 해석에 관한 연구", 한국산업안전학회 논문지, Vol. 19, No. 1, pp. 60-65, 2004.
  8. 최충석, 김향곤, "열 스트레스에 의한 비닐절연전선의 탄화 패턴 및 결정 구조의 변화", 대한전기학회논문지, Vol. 57P No. 3, pp. 332-337, 2008.
  9. 최충석 외 3, "직렬아크에 따른 도체의 산화물 증식 및 전압 파형 분석", 대한전기학회논문지, Vol. 55P No. 3, pp. 146-152, 2006.
  10. 최충석, "층간 단락된 3상 몰드변압기의 소손 패턴 및 금속 조직 해석", 한국안전학회논문지, pp. 86-91, 제25 권 제6호, 2010.
  11. Chung-Seog Choi et al, "Temperature Diffusion Distribution of Electric Wire Deteriorated by Overcurrent", IEEJ Trans. PE, Vol. 128, No. 1, pp. 194-198, 2008. https://doi.org/10.1541/ieejpes.128.194
  12. 김향곤 외 3, "비닐절연전선의 산화물 성장 특성과 화재조사에의 적용", 대한전기학회논문지, Vol. 56P, No. 1, pp. 37-44, 2007.