Particle-in-cell simulation on breakdown characteristics between bus-bars under circuit breaker interruption conditions in low voltage switchgear

The interruption process of circuit breakers in low-voltage switchgear always results in the formation of high-temperature gas, and the high-temperature gas will be emitted to the bus-bar terminals, which will lead to the inter-phase breakdown of the bus-bar in the switchgear. In this paper, a two-dimensional particle-in-cell/Monte Carlo collision simulation model has been proposed to simulate the gap breakdown between the bus-bars due to the high-temperature gas. The simulation results indicate that the inter-phase breakdown of the bus-bar is predominantly attributable to the high-temperature gas and the residual plasma emitted from the chamber room. The ions, upon striking the cathode, generate secondary electrons, and the electrons subsequently ionize the background gas, leading to electron multiplication. This process ultimately results in the breakdown of the inter-phase gap. When the gap does not meet the necessary breakdown conditions, the charged particles undergo gradual dissipation and disappearance. It is, therefore, proposed that the reduction in the gas temperature of the gap, in conjunction with the increase in the gap distance between the bus-bars, placed centrally within the bus-bar insulating divider, would be efficient methods of inhibiting the inter-phase breakdown of the bus-bars. Furthermore, it is hypothesized that the change of the chamfer of the bus-bar from a sharp corner to a rounded corner during the process of gap breakdown would also have a certain inhibition effect.