Numerical simulation of streamer discharge triggered by free metal particles in SF₆/N₂O gas mixtures within high-voltage equipment

Abstract In electrical equipment, partial discharge induced by metal particles is a prevalent issue that threatens the insulation of equipment. With its favorable environmental compatibility and insulating properties, N 2 O gas is considered a promising substitute for SF 6 . This study employs a two-dimensional plasma fluid dynamics model coupled with electrostatic and current modules to simulate the propagation process of positive streamer discharges from free metal particles in SF 6 /N 2 O gas mixtures under floating potential and highly non-uniform electric fields. Simulation results indicate that as the SF 6 mole fraction increases, the streamer head’s axial distributions of electron density, electric field, and reaction rates become steeper, with higher peak magnitudes. Among negative ions, the concentration of SF 6 − exceeds that of SF 5 − . At 40% SF 6 content, SF 6 − concentration surpasses N 2 O + concentration, F concentration dominates over SF 6 − . When the streamer propagates to within 0.1 mm of the cathode, at 40% SF 6 concentration, the streamer head thickness and propagation velocity exhibit increases by factors of 1.45 and 6.5 respectively compared to those at 10% SF 6 . Near the lower tip region, the positive and negative ion number densities for particles with minor-axis radii of 0.08 mm and 0.48 mm differ by nearly an order of magnitude.