Breakdown Characteristics of SF6 Gas under VFTOs in Non-uniform Field

초록

This paper describes breakdown characteristics of SF6 gas under very fast transient overvoltages (VFTOs) in the presence of metallic particles of gas-insulated switchgear (GIS).Breakdown voltage-time (V-t) and voltage-pressure (V-p) characteristics are stastically investigated with positive and negative VFTOs. As a result,the dependence of the V-t and V-p characteristics on the polarity of applied voltage is known to be appreciable and is closely related to the predischarge development mechanisms.It was confirmed that all the predischarges develop in a regime of stepwise leader extension.Basic predischarge development leading to breakdown against VFTOs are similar to the non-oscillating impulse voltages.The dependence of the V-t characteristics on the waveform of the negative applied voltage is noticeable.