Breakdown path and condition of air-insulated rod–plane gap with polymeric barrier inserted under alternating voltages

Abstract

In order to improve the insulating performance of air-insulated high voltage electrical apparatuses, solid barriers are always introduced in the interelectrode gaps. The breakdown paths and conditions of air-insulated rod-plane gaps in the range of 2–5 cm under alternating voltages were investigated for three different sizes of polyvinyl chloride barriers inserted at different gap positions. The breakdown processes were observed using two cameras placed in orthogonal directions, and two typical breakdown paths were captured. The statistical results showed that the occurrence probabilities of the two typical breakdown paths were related to the barrier position, but that the breakdown voltages were very similar in all breakdown events. Further, formulae to predict the breakdown voltage were deduced using a linear regression method. The results provide a reference for improving the insulation performance of gas–solid hybrid insulation systems based on the barrier effect as well as for modelling gas discharges in hybrid gaps.