Study on Power Frequency Breakdown and Decomposition Characteristics of SF6/N2 Gas Mixture

The SF6/N2 gas mixture is a key eco-friendly alternative to SF6 in power equipment. However, its insulation and decomposition behaviors under realistic conditions of varying pressure and electric field non-uniformity remain insufficiently studied. This study establishes an experimental platform to systematically investigate the power–frequency breakdown and decomposition characteristics of a 3:7 SF6/N2 mixture. Breakdown tests and critical field strength calculations were conducted under different pressures and electric field uniformities, followed by gas composition analysis. Results demonstrate that the proposed critical breakdown field strength method effectively predicts the mixture’s breakdown voltage. Furthermore, a range of decomposition products, including NF3, SOF2, CO2, and C2F6, were identified, whose concentrations generally decreased with rising pressure. These findings provide valuable experimental data and a predictive tool for optimizing the insulation design and condition monitoring of SF6/N2 gas-insulated equipment.