The induced effect of surface charge accumulation on DC flashover: from the sight of dynamic charging evolution

The surface charge accumulation on a spacer is a key factor in inducing flashover under DC voltage conditions. Different polarities of charge were preset on the insulator surface to investigate the influence of surface charge on flashover. Here, SiC/epoxy coatings were introduced to create different surface states of insulator, resulting in different degrees of charge accumulation, and the dynamic evolution of surface charge was measured as the voltage increased until flashover occurred. The results indicate that the insulator surfaces primarily exhibit homo-charge accumulation approaching flashover, and the increment of SiC contents in coating, as well as the homo-charge presetting, helps to increase the flashover voltage. Furthermore, by analyzing the evolutions of surface charge under different pre-set charge polarities, combined with the changes in field intensity near the high-voltage electrode during voltage elevation, correlation between preset charge, surface charge distribution approaching flashover, and flashover voltage was established. Therefore, based on the analysis of the mechanism of flashover induced by surface charge, the influence of different pre-charge polarities on this process was further revealed.