• 한국전기전자재료학회논문지
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• 제29권1호
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• pp.44-49
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• 2016

Studies on a $SF_6$-mixture and -alternative gas has been in progress to reduce the use of $SF_6$ gas as an insulation material of GIS (gas insulated switchgears). In this paper, we dealt with PD (partial discharge) characteristics in pure $SF_6$ and $N_2$, and their mixtures on aspects of insulation design and risk assessment for GIS. A POC (protrusion on conductor) and a POE (protrusion on enclosure) as the major defects were fabricated to simulate PD. We analyzed the DIV (discharge inception voltage), DEV (discharge extinction voltage), pulse magnitude, counts and phase distribution of PD pulse in $SF_6-N_2$ mixtures ($SF_6$ 100%, $SF_6$ 80%-$N_2$ 20%, $SF_6$ 50%-$N_2$ 50%, $SF_6$ 20%-$N_2$ 80%, and $N_2$ 100%) according to the IEC60270. The DIV, DEV as well as magnitude of PD pulse decreased on the POC as increase of $N_2$ ratio. For the POE, the DIV and DEV in $N_2$ ratio below 50% were the same voltages as those in $SF_6$ 100%. In this experiment, $SF_6$ 80%-$N_2$ 20% mixture could be considered with the equivalent insulation performance to a GIS.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권9호
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• pp.456-465
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• 2001

In this paper, breakdown voltages in $SF_6-N_2$ mixtures were experimentally investigated to understand characteristics of dielectric strength and physical phenomena in nonuniform field disturbed by a needle shape protrusion. The test voltages are the lightning impulse$(\pm1.2/44 \mus)$ and the damped oscillatory impulse$(\pm400 ns / 0.83 MHz)$ voltages which can be occurred by the operation of disconnecting switches in gas-insulated switchgears(GIS). The effects of the polarity and wave shape of the test voltages, and the gas pressure on the V-t characteristics were in detail examined. The V-t characteristic curves were measured in different two ways : (1) one is the method by taking the maximum voltage recorded at or prior to breakdown against the time to breakdown, that is, the Procedures recommended in IEC 60060-1, (2) the other is the method by taking the voltage at the instant of chopping against the time to breakdown. As a result, the V-t characteristics of $SF_6-N_2$ mixtures in nonuniform electric field were significantly affected by the polarity and wave shape of the applied voltages. The positive breakdown voltages resulted in lower breakdown voltages in the time ranges considered, and the V-t curves for the negative oscillatory impulse voltage were extended over the longer time range. For the lightning impulse voltages, the V-t curves obtained by IEC Pub. 60060-1 were nearly same with the V-t curves obtained by the voltage at the instant of chopping against the time to breakdown. It is clear that the actual breakdown voltages were much lower than the maximum voltages appearing at or prior to breakdown because of the displacement current produced as a result of the dV/dt during the oscillatory transient voltage app1ication. The scattering of the negative actual breakdown voltages was much larger than that of the positive.

• 한국철도학회논문집
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• 제20권2호
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• pp.203-209
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• 2017

전력공급의 안정성 및 신뢰도 향상을 위해 각종 전력설비의 예방진단에 관한 연구개발이 활발하다. 가스절연개폐장치와 변압기와 같은 단위 기기의 절연진단기술은 빠르게 발전하고 있으나, 전력케이블에 있어서는 단순히 결함의 유무와 부분방전을 측정할 뿐, 세부적 특성에 대해서는 거의 연구되고 있지 않다. 따라서 본 논문에서는 XLPE 케이블에서 보이드의 크기와 위치에 따른 부분방전 특성과 결함의 위치추정에 관한 연구를 수행하였다. 보이드의 크기 및 위치에 따른 4종의 결함계를 모의하였으며, 부분방전펄스는 주파수 대역 150kHz~30MHz의 고주파변류기로 검출하였다. 실험결과, 도체에 인접한 결함일수록 방전전하량이 크고, 정극성에 비해 부극성의 방전펄스 수가 약 20% 많게 나타났다. 또한 TDR 방법으로 결함위치를 산출하였으며, 50m 케이블에서 1m 이내로 결함의 위치를 추정할 수 있었다.