Study of a Nonequilibrium Plasma Model of Surface Discharge and the Influencing Factors

The ultrafast mechanical switch is one of the core technologies in hybrid high-voltage direct current breakers. However, the insulation between contacts may suffer surface insulation failure at moments of large current interruption. Studies show that surface charges play an important role in surface insulation failure. To date, there is still a lack of complete physical understanding of the rules governing the generation, migration, and accumulation of surface charges. In this paper, we present a nonequilibrium plasma model to investigate the development rules of stage transformation (corona discharge, streamer discharge, and spark discharge) of surface discharge. Surface charge distributions considering the effects of voltage amplitude and insulation materials are also discussed. The results show that the stages of surface discharge can be identified from the discharge current. The surface charge will increase under a continuous voltage, and most of the surface charge density is within 100 μC/m
²
. Increasing the voltage amplitude is not conducive to the accumulation of positive charges. However, the surface charge density and discharge current increase along with the voltage amplitude. The discharge current variations of different materials are basically consistent. The surface charge density may be positively associated with the relative dielectric constant, whereas it is difficult to judge the direct relationship between the surface charges and discharge current.