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

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, N2O gas is considered a promising substitute for SF6. 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 SF6/N2O gas mixtures under floating potential and highly non-uniform electric fields. Simulation results indicate that as the SF6 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 SF6- exceeds that of SF5-. At 40% SF6 content, SF6- concentration surpasses N2O+ concentration, F concentration dominates over SF6- . When the streamer propagates to within 0.1 mm of the cathode, at 40% SF6 concentration, the streamer head thickness and propagation velocity exhibit increases by factors of 1.45 and 6.5 respectively compared to those at 10% SF6. 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.