Breakdown Characteristics of a Long Air Gap Containing a Floating Conductor Under Positive Switching Impulse

Experiments on the breakdown characteristics of a long air gap containing a floating conductor under switching impulse are carried out to address issues in live-line work engineering. The effects of gap distance, floating conductor structure, wavefront time, and high altitude on breakdown voltage are investigated, respectively. The results show that a floating conductor with sharp protrusions reduces the breakdown voltage and produces the lowest breakdown voltage area (LBA). The maximum reduction rate of the breakdown voltage and the position of the LBA vary with the gap distance. The position of the LBA is also related to the floating conductor structure. The results indicate that different floating conductor structures with similar electric field distortions have a similar effect on the breakdown voltage. For the effect of wavefront time on breakdown characteristics, the results show that the breakdown voltage under switching impulse with a long wavefront time is higher than that under a standard switching impulse. For the effect of high altitude, the results show that the LBA at high altitude is different from that at low altitude, and the high-altitude breakdown voltage corrected using the International Electrotechnical Commission (IEC) altitude correction method is not exactly the same as the actual experimental results.