• 한국전기전자재료학회논문지
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• 제13권1호
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• pp.85-93
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• 2000

In this paper, the predischarge propagation processes of SF\ulcorner gas stressed by impulse voltages under nonuniform electric field perturbed by a needle protrusion are described. The statistical and formative time-lags and the time interval between leader pulses were investigated on the basis of the predischarge current measured in the gas pressure range of 0.1~0.5 MPa. The predischarge current is closely related to the waveform, amplitude and polarity of applied votages, the gas pressure and the gap geometry. Both the positive and negative predischarge processes in nonuniform electric field develop in a regime of stepwise leader propagation leading to electrical breakdown. The mean of the time interval between leader pulses gives about a factor of 10 higher for the negative than for the positive leader current puls-es. According as the gas pressure increases, the statistical time-lag was almost unchangeable, but the formative time-lag was gradually decreased.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권6호
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• pp.288-295
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• 2001

Predischarges in nonuniform electric field stressed by lightning impulse voltagesin SF(sub)6-$N_2$mixtures are initiated by streamer coronas. Due to field ehnancement at a protrusion point of electrodes new ionization processes occur and a precursor, which leads to a first leader, is created. The leader proceeds step by step to the opposite electrode and the final jump bridges the test gap. It was found that the predischarge is propagated with a leader mechanism of stepwise expansion from the predischarge current waveforms measured by a shunt. The predischarge current is closely related to the amplitude and polarity of applied voltages, the gas pressure and the gap geometry. The time intervals between step leaders for the positive and negative polarities were inversely proportional to V.P$^2$. When the gas pressure increases in the positive polarity, statistical time lag to statistical time lag to streamer corona inception increase slightly, but the formative time lag to flashover is significantly decreased.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2140-2142
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• 2005

This paper presents the experimental results on the preliminary breakdown characteristics under a highly non-uniform electric field in $SF_6/CO_2$ gas mixtures. The impulse preliminary breakdown developments are investigated by the measurements of corona current and light emission images. As a result, the preliminary breakdown development mechanisms for both positive and negative polarities are same. The first streamer corona is initiated at the tip of needle electrode, and the leaders develop with a stepwise propagation and bridge the test gap. The pause time of leader pulses in the positive polarity is significantly shorter than that in the negative polarity. Also, the time interval between the first streamer corona onset and breakdown in the negative polarity was much longer than that in the positive polarity The discharge channel paths in the positive polarity were zigzag. On the other hands, the leader channel in the negative polarity was thicker than that in the positive polarity.

• 조명전기설비학회논문지
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• 제20권1호
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• pp.85-90
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• 2006

본 논문은 불평등 전계의 $SF_6/CO_2$혼합기체 중에서 전구방전특성에 대한 실험결과를 제시한다. 임펄스 전구방전 진전을 코로나 전류와 방전광 이미지의 측정으로 조사하였다. 정 부극성의 전구방전 진전메커니즘은 기본적으로 같았으며, 초기스트리머코로나는 침전극의 끝단에서 발단되어 계단상으로 진전하는 리더에 의해 시험갭을 교락시킨다. 정극성에서 리더펄스의 휴지시간은 부극성에서보다 매우 짧았다. 또한 부극성에서 초기스트리머코로나와 절연파괴사이의 시간간격은 정극성에서보다 매우 길게 나타났다. 정극성에서 방전채널경로는 임의적으로 나타났으며, 부극성에서 리더 채널은 정극성에서 보다 굵고 밝게 나타났다.