Partial discharges induced by free metal particles impair the insulation performance of high-voltage electrical equipment. Owing to its environmental benefits, cost-effectiveness, and excellent dielectric properties, the SF6/CO2 gas mixture has emerged as a promising alternative for gas-insulated applications. This study establishes a two-dimensional plasma fluid model, utilizing the finite element method to self-consistently couple the current and electrostatic fields for simulating the discharge of millimeter-sized particles in an SF6/CO2 mixture at 220 kV. The results indicate that as the proportion of SF6 increases from 10 to 30%, the streamer propagation velocity decreases and the breakdown time prolongs. The streamer head exhibits a sharp rise in electric field strength and electron density. This indicates that SF6’s strong electronegativity suppresses electron avalanche development, thereby promoting the accumulation of space charge, which in turn leads to more pronounced electric field distortion. Analysis of ion distribution shows a decrease in CO₂^ + density, while the densities of SF₆^ - and SF₅^ - increase, indicating a shift in the discharge mechanism from being dominated by CO2 ionization to a synergistic mechanism dominated by SF6 adsorption and ionization. This study achieves real-time solving of the floating potential of metal particles through multi-physics coupling and systematically elucidates the physical mechanisms of streamer initiation by particles in mixed gases with different ratios, providing a theoretical basis for the formulation of eco-friendly insulating gas mixtures and engineering insulation design.
Bing et al. (Wed,) studied this question.