Quantitative Analysis on the Influence of Surface Charges on Flashover of Insulators in SF6

In this paper, the influence of surface charges is quantitatively analyzed based on the study of surface charge distribution under DC voltage and flashover characteristics of insulators under superimposed voltage of DC and lightning impulse. It is found that when DC and impulse voltage are in the same polarity, surface charges weaken the electric field along the insulator surface and flashover voltages under superimposed voltage increases. When DC and impulse are in the opposite polarity, surface charges enhance the electric field along the insulator surface, and flashover voltages will decrease. The calculation results of the electric field along the flashover path show that the changing rate of the maximum field strength is approximately equal to the changing rate of flashover voltage, which proves that the influence of surface charges on flashover characteristics of insulators mainly depends on their distortion of the electric field.