Dynamic Evolution of Surface Charge on SiC/Epoxy Coating and Its Effect on Surface Withstand Ability at DC Voltage

In order to clarify the mechanism of how surface coatings affect surface withstand ability of insulator at dc voltage, the study of surface flashover on SiC/epoxy-coated insulator was conducted and a method that how to determine the approaching flashover moment (AFM) was proposed. Based on the plate-insulator and finger-shaped electrode arrangement, the flashover characters, as well as dynamic surface charge distribution during the applied voltage rising, were studied under two kinds of charging methods, i.e., compact and uncompact contact condition at electrode–insulator interface. It was found that the surface flashover voltage was increased with the increment of SiC contents in coatings. The dynamic surface charging evolution confirms that homocharge accumulation was the main charging phenomenon approaching the flashover occurrence, and the evolution mechanism of dynamic surface charge distribution was also explained. In addition, the surface electric field at the AFM was calculated; then, the effect of charge accumulation on flashover voltage was analyzed. At last, from the sight of charge accumulation, the influence of SiC contents on surface withstand ability at dc voltage was discussed.