Investigation on the Dielectric Properties of Hot CO₂ and CO₂-based Gas Mixtures Based on the Boltzmann Equation Analysis

CO₂ is a potential alternative for SF₆ in the high voltage circuit breaker. In this paper, the critical re-duced electric field strength (E/N)_cr of CO₂, CO₂-O₂, CO₂-N₂, CO₂-CH₄ and CO₂-H₂ at different mixing ratios, pressures and temperatures (300~4000 K) have been calculated. The species composition of CO₂ gas mixtures was calculated based on the Gibbs free energy minimizing to pick out the main species. Then the (E/N)_cr of CO₂ gas mixtures at different conditions were derived by solving the two term approximation of Boltzmann equation. The re-sults indicate that the (E/N)_cr of CO₂-O₂, CO₂-H₂ and CO₂-CH₄ are higher than that of other mixture gases. The fun-damental data of the insulation properties of CO₂ and its mixtures under high temperature are obtained, which pro-vides a theoretical basis for the search of substitute gases for SF₆.