Partial discharges in SF₆ gas filled void under standard oscillating lightning and switching impulses in uniform and non-uniform background fields

Behaviors and characteristics of partial discharges in SF₆ gas filled void are investigated under oscillating lightning impulse voltage (OLI) and switching impulse voltage (OSI). The negative and positive PD sequences under impulses are described and analyzed under the applications of uniform and non-uniform background fields. Four types of discharge pulses in sequences are distinguished by their magnitudes, waveforms and time interval and well interpreted by a charge memory physic model. The distribution of PD points under OLI and OSI in normalized phase range (φN, Im) are proposed to describe the occurrence of PD under periodic oscillation impulses statistically. It is indicated that the discharges with low magnitudes are distributed in the relative large ranges of phase and the discharges with high magnitudes are mainly distributed in the relative narrow ranges of phase. By experimental results, the influences of the gas pressure and the void dimension ratio are studied and it is concluded that both the increases of these two factors could bring the obvious restrictions on PD activity under oscillating impulses.