PIC/MCC simulation of post-arc reignition with consideration of cathode temperature distribution and droplets in vacuum circuit breakers

To study the restrike process of vacuum circuit breaker (VCB), this paper establishes a two-dimensional Particle-in-Cell / Monte Carlo Collision (PIC/MCC) model applicable to the post-arc breakdown process, and conducts a simulation investigation on the post-arc breakdown phenomenon during the evolution of residual plasma after the termination of the vacuum arc burning phase. The simulation incorporates the thermal electron emission process of the post-arc cathode (anode in arc stage), collision behaviors between electrons and copper atoms/ions, and charge exchange processes. Meanwhile, this paper further studies the influence of post-arc cathode temperature distribution on the post-arc restrike process, and based on the basic post-arc restrike model, introduces metal droplets into the gap to study their mechanism of action on post-arc restrike. The simulation results reveal that a higher post-arc cathode temperature and a more uneven temperature distribution significantly increase the probability of restrike. Furthermore, metal droplets in the post-arc gap not only generate thermal electrons but also cause electric field distortion in the gap, thereby making arc restrike more prone to occur. The probability of post-arc restrike in VCB is significantly enhanced when the number of metal droplets increases, their radius enlarges, and their positions are closer to the cathode center.