Effects of DC and pulse voltage combination on surface charge dynamic behaviors of epoxy resin

Epoxy resin is widely used in disc-type spacers of gas insulated switchgear (GIS). Surface flashover related to the existence of surface charge often occurs on the spacer, which is a great threat to the application of HVDC GIS and the safety of entire grid. Moreover, the influence on surface charge dynamic behavior under pulse voltage produced by switch overvoltage, accompanying with the DC voltage, is still unclear. In order to research the comprehensive effect of DC and pulse voltage on surface charge behavior, in this paper, epoxy resin sample was charged by a corona discharge system and the charge distribution was measured by an electrostatic voltmeter. The results are obtained from the research of different pulse amplitudes and pulse polarities. When DC and pulse voltage with the same polarity are applied, smaller pulse voltage would push the original charges away, resulting in the decrease of initial surface potential. But a big pulse voltage could increase the surface potential. The speed of surface charge dissipation has an opposite tendency. When the pulse polarity becomes the opposite of DC voltage, surface potential at the sample center will be a heteropolar value at the beginning and then it gradually becomes consistent with the initial polarity. In addition, the surface charge change rate will rise with the increase of heteropolar pulse voltage. The Trap energy distributions were used to analyze charge decay process in the last section.