Kinetic model of prestrike arc in vacuum interrupters

Abstract

During the closing operation of a capacitive load by a vacuum interrupter, there is always a prestrike arc. An inrush current with high frequency and high amplitude flows through the prestrike arc. This prestrike arc with a high energy density destroys contact surfaces locally, resulting in welding between the mated contacts. Consequently, the opened destroyed surfaces, which enhance the local electric fields and bring metal particles into the contact gap, increase the restrike probability of the interrupter under a DC recovery voltage. The objective of this paper is to establish a kinetic model to investigate the characteristics of prestrike arcs and the energy fluxes to the electrodes during closing capacitive loads. The Particle in Cell-Monte Carlo Collision(PIC-MCC) method was adopted in this model to describe this high density plasma within a small gap. The distance between the contacts was set to 1μm. Three different electrode temperatures were set to investigate their influence on results. Electron-atom elastic collision and electron impact ionization were considered in the model. According to the results, the plasma density, current density and energy fluxes to electrodes increased with electrode temperature. The length of arc column also increased with electrode temperature. Electron current was main component of the current. Electron energy flux was less than ion energy flux at cathode, while it was just the reverse at anode.