Numerical simulation of insulator surface discharge induced by suspended metal particle in C4F7N/CO2 mixtures

Abstract

Possessing favorable environmental friendliness and excellent insulating properties, C4F7N has attracted extensive research attention and is considered a promising alternative to SF6. This paper constructs a two-dimensional plasma fluid model and employs finite element simulation to explore surface discharge triggered by free metallic particles in C4F7N/CO2 gas mixtures. The spatiotemporal evolution of electron density, ion density, electric field strength, electron energy, and breakdown voltage under different mixing ratios is analyzed. Simulation results reveal that elevating C4F7N content slows discharge propagation and extends breakdown duration. The duration from discharge inception to surface flashover under 5% C4F7N concentration is roughly half that under 10% concentration, and 18% C4F7N presents a prominent suppression effect on discharge development. Ion distribution analysis shows that CO2+ dominates the discharge at concentrations of 5% and 10%, and obvious charge accumulation occurs at metallic particle tips and ground electrodes. When the concentration rises to 18%, the proportion of CO2+ declines, while the fractions of C4F7N−increase. Charge accumulation only appears at particle tips, demonstrating that the discharge mechanism shifts from CO2 electron-impact ionization to the joint dominance of C4F7N adsorption and impact ionization. Through electrostatic-current field coupling, this work clarifies the microscopic mechanism of surface discharge varying with C4F7N concentration, offering theoretical references for insulation design and gas proportion optimization of electrical equipment.