Fire Science and Engineering (한국화재소방학회논문지)

Korean Institute of Fire Science and Engineering (한국화재소방학회)
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Carbonization Patten and Operation Characteristics of a 1Φ 2 W MCCB Damaged by PCITS

PCITS에 의해 소손된 1Φ 2 W MCCB의 탄화 패턴 및 작동 특성

  • 이재혁 (전주대학교 소방안전공학과) ;
  • 최충석 (전주대학교 소방안전공학과)
  • Received : 2014.05.07
  • Accepted : 2014.10.17
  • Published : 2014.10.31
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Abstract

The purpose of this study is to analyze the damage pattern when overcurrent is applied to a thermal magnetic type molded case circuit breaker (MCCB) using a Primary Current Injection Test System (PCITS). When an overcurrent of 150 A was applied to the PCITS for 5 seconds with the trip bar of an MCCB being damaged, it was found that the surface of the temperature control device (bimetallic strip) positioned at the right was significantly carbonized. When an overcurrent of 300 A was applied to the PCITS for 5 s under the same conditions, the entire temperature control device was deteriorated, becoming flattened and in close contact with the MCCB. When an overcurrent of 450 A was applied to the PCITS for 5 s, the coil of the temperature control device was melted and disconnected. In addition, it was observed that the contacts, the enclosure and upper cover were deformed and there was a trace of carbonization on them. When approximately 3 s had elapsed after an overcurrent of 600 A was applied, white smoke occurred inside the MCCB and a flame was radiated out, after which the overcurrent supply stopped with "phutt" (whomp) sound. It was observed that when the same type of MCCB is damaged by a general flame, the surfaces of its handle, terminal, arc divider (extinguisher) and temperature control device were carbonized uniformly. In addition, it was found that the trip bar of the operating mechanism was melted down and the metal operation pin was moved while being tripped.

본 연구에서는 대전류공급장치시스템(PCITS)을 이용하여 열동전자식 배선용차단기(MCCB)에 과전류를 인가하였을 때 소손된 패턴을 해석하는 데 있다. MCCB의 트립바가 소손된 상태에서 PCITS로 과전류 150 A를 5 s 동안 흘렀을 때 우측에 위치한 온도 조절 장치의 표면이 심하게 탄화되었다. 동일한 조건에서 300 A의 과전류를 5 s 동안 흘렸을 때 온도 조절 장치의 전체가 열화(劣化)되어 납작하게 밀착되었다. 과전류 450 A를 5 s 동안 흘렸을 때 온도 조절 장치의 코일은 융융 및 단선이 발생하였다. 또한 접점, 외함 및 상부 덮개 등에서 탄화 흔적 및 변형이 확인되었다. 과전류600 A를 공급하고 3 s 정도가 경과되었을 때 MCCB의 내부에서 흰색 연기가 발생하였고, 불꽃이 외부로 방사되었다. 그리고 탁(딱)하는 소리와 동시에 과전류의 공급이 중단되었다. 동일한 MCCB를 일반 화염으로 소손시켰을 때 작동 손잡이, 단자, 소호 장치 및 온도 조절 장치 등의 표면에 탄화가 고르게 형성된 것을 알 수 있다. 또한 작동 기구부의 트립바는 녹아 흘러 내렸으며, 작동 금속핀은 트립 상태로 이동된 것이 확인된다.

Keywords

References

  1. International Electrotechnical Commission, "IEC 60898-1, 60898-2" (2011).
  2. Korean Standards Association, "KS C 8321, 8111", Korean Agency for Technology and Standards (2008).
  3. Korean Standards Association, "KS C IEC 6060947-1", Korean Agency for Technology and Standards (2008).
  4. Korean Standards Association, "KS C IEC 6060947-2", Korean Agency for Technology and Standards (2008).
  5. C. S. Choi, H. W. Kim, K. S. Lee, Y. S. Lim, C. H. Lee and J. H. Chung, "Electrical Fire Engineering", Donghwa Technology Publishing Co., pp. 193-197 (2004).
  6. C. S. Choi, "Firefighting and Electrical Installation", Donghwa Tech. Publishing Co., pp. 407-413 (2013).
  7. C. S. Choi, "Analysis of the Damage Patterns and Metal Structure of 3 Phase Mold Transformers to which Interlayer Short-circuits have Occurred", Journal of the Korean Society of Safety, Vol. 25, No. 6, pp. 86-91 (2010).
  8. C. S. Choi, "Analysis of the Causes of Accidents Related to 3 Phase 170 kV Gas Insulated Switchgears (GIS) and Preventive Measures", Journal of the Korean Society of Safety, Vol. 26, No. 4, pp. 41-46 (2011).
  9. D. O. Kim, K. Y. Lee, H. W. Moon, H. K. Kim and C. S. Choi, "Fire Hazard Analysis of MCCB Terminals in Resistance Load by Connection Failure", Proceeding of 2007 Spring Annual Conference of the Korean Institute of Electricsl Engineering, pp. 88-90 (2007).
  10. D. O. Kim, K. Y. Lee, H. W. Moon, H. K. Kim and C. S. Choi, "Damage Properties and Overheat Detection Techniques of Connection Parts of MCCB and Terminal Block", Journal of Korean Institute of Fire Science & Engineering, Vol. 22, No. 4, pp. 54-60 (2008).
  11. D. O. Kim, D.. W. Kim, H. K. Kim and C. S. Choi, "The Example of Electrical Fire due to the Tracking on the Circuit Breaker", Proceeding of 2005 Fall Annual Conference of Korean Society of Forensic Science, pp. 213-217 (2005).
  12. J. H. Lee, "Study on the Examination of the Damage Patterns of a Thermal Magnetic MCCB and its Operation Mechanism", Jeonju University, pp. 21-25,49-52 (2013).
  13. J. H. Lee and C. S. Choi, "Damage Pattern and Operation Characteristics of a Thermal Magnetic Type MCCB according to Thermal Stress", Journal of the Korean Society of Safety, Vol. 28, No. 3, pp. 69-73 (2013). https://doi.org/10.14346/JKOSOS.2013.28.3.069