Modeling of the effect of humidity on air–dielectric interface flashover in non-uniform electric field under nanosecond pulse

Abstract

To illustrate the effect of humidity on air–dielectric interface breakdown under non-uniform electric fields induced by metal particles, a coupled fluid and kinetic simulation method is employed. The results show that the development of streamer discharge along the dielectric surface in humid air both is promoted under high-voltage positive and negative polarity nanosecond pulse, consistent with simulation and experimental findings. The effective ionization rate in humid air is larger than that in dry air when the electric field is large enough. Thus, the development of discharge in humid air is faster under a strong electric field. To further investigate mechanism of streamer propagation, the gas discharge under non-uniform electric field is simulated. The simulation results show that as the electric field decreases, the streamer propagation process transitions from being governed by the effective ionization rate at the streamer head to being governed by humidity-induced electron loss and conductivity decay in the channel. Consequently, streamers propagate faster in humid air under strong electric fields, whereas they propagate faster in dry air under weak electric fields.