• Title/Summary/Keyword: Time interval between leader pulses

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Analysis of Predischarge Processes of $SF_6$ Gas Stressed by lmpulse Voltages under Nonuniform Electric Field (불평등전계중에서 임펄스전압에 대한 $SF_6$ 기체의 전구방전과정의 분석)

  • 이복희;이경옥;이창준;백승권
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.1
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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.

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Predischarge Phenomena in Nonuniform Fields Caused by Lightning Impulse Voltages in SF(sub)6-$N_2$Mixtures (SF(sub)6-$N_2$혼합가스중에 뇌임펄스전압에 의해 형성된 불평등전장에서의 전구방전현상)

  • 이복희;이경옥;백승권
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.50 no.6
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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.

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Characteristics of lightning impulse preliminary breakdown discharge under non-uniform electric field in $SF_6/CO_2$ mixtures (불평등전장에서 $SF_6/CO_2$ 혼합기체의 뇌임펄스 전구방전특성)

  • Lee, B.H.;Oh, S.K.;Baek, Y.H.;Ahn, C.H.;Jeon, D.K.
    • Proceedings of the KIEE Conference
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    • 2005.07c
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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.

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Characteristics of lightning Impulse Corona Discharges in SF6/CO2 Mixtures (SF6/CO2혼합기체 중에서 뇌임펄스코로나방전의 특성)

  • Lee, Bok-Hee;Baek, Young-Hwan;Oh, Sung-Kyun;Ahn, Chang-Hwan
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.1
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    • pp.85-90
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    • 2006
  • This paper presents experimental results relating to the preliminary breakdown characteristics in $SF_6/CO_2$ gas mixtures under a highly non-uniform electric field. The impulse pre-breakdown developments are investigated by the measurements of corona current and light emission images. As a result, the preliminary breakdown development mechanisms for both the positive and negative polarities were fundamentally same. The first streamer corona was initiated at the tip of needle electrode, and the leaders developed with a stepwise propagation and bridged the test gap. The pause time of leader pulses in the positive polarity was 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 path in the positive polarity was zigzag, and the leader channel in the negative polarity was thicker and brighter than that in the positive polarity.