Discharge Characteristics of CF3SO2F/N2 Gas Mixture in Non-Uniform Fields Under Power Frequency AC Voltage

CF₃SO₂F (Trifluoromethanesulphonyl Fluoride) has emerged as a promising SF₆ (Sulfur Hexafluoride) alternative gas, yet its insulation characteristics under non-uniform electric fields is unclear. This paper investigates the breakdown and surface flashover properties of CF₃SO₂F/N₂ mixtures under power frequency AC voltages in non-uniform fields, with comparative analysis against SF₆ under identical conditions. The results demonstrate that increased pressure enhances insulation strength for all gas mixtures, under extremely non-uniform electric fields, the breakdown voltage of SF₆ exhibits a significant saturation trend with increasing gas pressure, whereas the saturation phenomenon is relatively less pronounced in CF₃SO₂F/N₂ mixtures. For surface flashover, the saturation behavior of CF₃SO₂F/N₂ mixtures with rising pressure is more marked compared to SF₆. The CF₃SO₂F/N₂ mixture approaches the gap insulation performance of SF₆ more readily (requiring only about 0.2 MPa gas pressure), but shows a greater discrepancy in surface insulation performance (needing approximately 0.4 MPa gas pressure). Post-flashover characterization via Fourier Transform infrared spectroscopy, Scanning Electron Microscope and Energy Dispersive Spectroscopy reveals flashovers in SF₆ leads to extensive ribbon-like discharge channels with lots of erosions on the epoxy resin surface, while flashovers in CF₃SO₂F/N₂ mixtures produce only discrete spot-like damage with relatively few erosions.