Dielectric breakdown characteristics of the rod-plane electrode system in SF 6 gas under oscillating impulse voltage

Gas insulated switchgear (GIS) has been widely used in electric power system for its high reliability and the small size. And considering the transportation difficulty GIS is always assembled in field. The AC withstand voltage testing is used on the spot to check the insulation condition of GIS, but it is not enough to inspect all the defects inside GIS. So impulse voltage testing is required. But it is not easy to carry out the impulse voltage testing for the sake of the huge size of impulse voltage generator. IEC 60060-3 recommends the oscillating impulse voltage waveform as the field testing waveform for its high efficiency. The breakdown characteristics of SF 6 gas are still not clear under oscillating impulse voltage. This paper aims to present the breakdown characteristics of rod-plane electrode model in SF6 under oscillating voltage waveform. The oscillating lightning impulse voltage (OLI) with the frequency of 300 kHz is adopted as the testing waveform while the distance of rod-plane electrode is 3.2mm. The standard lightning impulse (SLI) voltage is also adopted as a reference waveform. The breakdown voltage-time (V-t) curves are illustrated in this paper. Results show the time lag under oscillating voltage is longer than that of the standard impulse voltage. Besides the oscillating characteristics of impulse voltage waveform have great influence on the breakdown characteristics of SF 6 .