Simulation and Analysis of the Breakdown Process of Surface Flashover Triggered Vacuum Switch

Improvements to the design parameter selection of surface flashover triggered vacuum switches (STVSs) can be effected by a more informed understanding of the dynamic evolution characteristics of plasma in the triggering process of STVS and by exploring the triggering mechanism. The electrical breakdown process is a prerequisite for the occurrence and development of the steady-state arc, which determines the initial plasma characteristics of the steady-state arc. Therefore, this article adopts the method of combining the particle model and fluid model. In this article, a model that more completely describes and demonstrates the physics of the STVS triggering process is presented. The generation and evolution behavior of initially charged particles, the phase transition behavior of the micro-spot on the anode surface, and the formation and breakdown behavior of plasma during the breakdown of the main gap are simulated. Simulation results indicate that when the plasma extends to the cathode surface, the electron density reaches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.4\times 10^{1}6$</tex-math> </inline-formula> m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup>, signifying the formation of a discharge channel. This demonstrates a fundamental transition of the main gap from a vacuum-insulated state to a conductive state. Following discharge channel formation, the electric field distribution near the cathode becomes significantly distorted. The local field strength rapidly increases to the critical breakdown threshold for field emission (FE), leading to successful gap breakdown. The physical mechanism of triggering electrical breakdown in STVS is systematically revealed through multiphysics coupling simulation. The research findings can offer a significant theoretical foundation and technical support for the optimization design of high-stability and low-jitter STVS products.