Mechanism of the Effect of Micro-Water on the Thermal Decomposition Characteristics of C₄F₇N/CO₂/O₂ Gas Mixture

The C4F7N/CO2/O2 ternary gas mixture, with its excellent environmental and insulating properties, has emerged as one of the most promising alternatives to SF6 and has seen initial applications in global power systems. Currently, there is limited research on the stability of C4F7N/CO2/O2 in equipment under long-term operation with micro-water content. This study uses reactive molecular dynamics simulations, using ReaxFF forcefield, to investigate the effect of water (up to 2%) on the thermal decomposition characteristics of C4F7N/CO2/O2 at the microscopic level. Additionally, thermal decomposition experiments of C4F7N/CO2/O2 under different micro-water concentrations were conducted to analyze the relationship between decomposition products and micro-water content. When the micro-water concentration is below 1.6%, H2O promotes the generation of O radicals, increasing the decomposition of C4F7N. However, as the H2O concentration increases further, the large amount of generated OH radicals consumes O radicals, inhibiting the main decomposition reactions of C4F7N. Experimental results show that the main thermal decomposition products of the gas mixture are CF4, C3F8, C3F6, C2F6, and CHF3. The findings of this study provide theoretical support and technical foundation for enhancing the reliability of C4F7N/CO2/O2 insulation equipment in long-term engineering applications.