A novel theoretical approach for investgating the mechanism of non-uniform charge deposition on dielectric surface induced by secondary electron avalanche in vacuum flashover

Abstract

In previous theoretical studies of vacuum surface flashover, zero-dimensional models were typically employed. It was assumed that only the applied electric field existed tangentially along the insulator surface, and the positive charges deposited on the dielectric surface were uniformly distributed along the tangential direction. However, experimental observations have revealed that the deposited charges on the dielectric surface exhibit a non-uniform distribution. By employing the concept of image charges, this paper proposes a novel theoretical approach that effectively explains the mechanism responsible for this non-uniform distribution of deposited charges. Furthermore, a theoretical criterion is proposed, suggesting that the maximum electric field strength near the cathode tends to be the same during flashover breakdown for the same insulating material. Based on this, a rapid calculation and scaling model for the flashover breakdown voltage of insulators with different lengths has been developed, which can provide fast predictive assessment for engineering applications. Comparisons with particle-in-cell (PIC) simulations and experimental results verify the correctness and reliability of the proposed theoretical method and rapid calculation model.