Effect of the DC-AC Switching Electric Field on Surface Electrical Properties of GIS Epoxy Spacer

This paper explores the behavior of charge transport and the surface electrical properties of epoxy spacers within high voltage alternating current (HVAC) gas-insulated switchgear (GIS), which may be exposed to the DC-AC switching electric field at the end of DC ice-melting. Simulation and experimental results reveal that increasing DC voltage and duration enhance charge accumulation at the gas-solid interface, whose polarity aligns with the electrodes. When the electric field transitions to AC, charge accumulation occurs gradually during the half-cycle where the voltage polarity matches the charge polarity. However, during the half-cycle of opposite polarity, the probability of flashover increases dramatically. Positive polarity DC charging leads to greater charge accumulation and more severe electric field distortion than negative polarity, thereby increasing the risk to the insulation performance.