Impulse partial discharge and breakdown characteristics of rod-plane gaps in N2/SF6 gas mixtures

Impulse partial discharge (PD) and breakdown (BD) characteristics of rod-plane gaps in N₂/SF₆ gas mixtures were investigated for different gap geometry, gas pressure and SF₆ gas content. Experimental results revealed that the 50% probability breakdown voltage increased with gas pressure, which agreed with the theoretical values with consideration of discharge time lag for impulse voltage application. For the calculation of discharge inception voltage, the volume-time theory was successfully applied to the N₂/SF₆ gas mixture. Furthermore, impulse PD light emission image was observed together with PD current pulse and light intensity waveforms. The long discharge with stepwise propagation and double-peak PD pulses could be observed, which corresponded to the streamer/leader transition leading to breakdown.