Simulation research on surface charging phenomena across solid dielectrics prior to flashover in vacuum

Prior to flasshover across solid dielectrics under steady-state high voltage excitation in vacuum, there are charging phenomena occurring on insulator surface, which significantly affect the developing process of flashover. In this paper, based on the secondary electron emission avalanche model (SEEA) and Monte Carlo simulation method, the theoretical analysis of surface charge density on insulation surface is made. A two-dimensional Mont Carlo simulation on surface charge accumulation under DC voltage excitation is provided. The results reveal that surface charging process can be divided into three stages including initial accumulation, fast multiplication and final stable stage. The positive charges exist in a small surface region near the cathode. While the flashover process develops, positive charges accumulate near the anode and the amount of positive charges is an order of magnitude larger than before. With flashover process developing, the peaks of positive charges move toward cathode. In the final stage, the SSEE phenomena are achieved and surface charges are invariable and reach up to a stable distribution.