Surface Charge Distribution Measurement before and after DC Flashover: A Novel Insight to the Influence of Surface Charge on Flashover Voltage

In this paper, epoxy resin as well as its nanocomposites with Al2O3 as the filler has been employed as test sample to investigate the surface charge distribution features before and after DC flashover. Electrical charges were introduced on sample surface by means of a pair of finger-shaped electrodes which were stressed with DC voltage superimposed by repetitive pulses. DC flashover test was then carried out to examine the influence of surface charge on flashover voltage. Both charge distribution before and after the flashover was measured. It was found that the presence of surface charge reduced the DC flashover voltage. Maximum charge density on the surface after flashover was even higher than that before flashover. It is proposed that although charges were pre-deposited by the superimposed voltage, the voltage rising period of DC flashover test certainly introduced more charges onto the sample surface, which may has much serious influence on the flashover phenomena. Surface charge distribution just prior to flashover should be measured in the future to further understand the surface charge effect on DC flashover of polymer insulating materials.