Insulation Characteristics of C3F8 Ternary Gas Mixtures from Electron Transport Parameters and Microscopic Properties

Abstract

In order to study an alternative SF6 gas medium, molecular theory and density functional theory (DFT) were used to analyze $\mathrm{C}_{3}\mathrm{F}_{8}$ as a substitute for SF 6 gas from microscopic properties. This paper aimed to adopt the Boltzmann equation method to calculation the electron transport coefficients and synergistic effect of $\mathrm{C}_{3}\mathrm{F}_{8}/\text{CF}_{3}\mathrm{I}/\text{CO}_{2}$ ternary gas mixtures, and compared with $\mathrm{c}-\mathrm{C}_{4}\mathrm{F}_{8}/\text{CF}_{3}\mathrm{I}/\text{CO}_{2}$ of same proportion. The results indicate that when E/N is lower than 400Td, the performance of $\mathrm{C}_{3}\mathrm{F}_{8}$ gas mixtures is better than that of $\mathrm{c}-\mathrm{C}_{3}\mathrm{F}_{8}$ gas mixtures in terms of diffusion coefficient and electron drift velocity. When the proportion of $\mathrm{C}_{3}\mathrm{F}_{8}$ is less than 7%, the insulation strength of gas mixtures is higher than that of $30\%\mathrm{SF}_{6} /70\%\mathrm{CO}_{2}$ gas mixtures. As for synergistic effect, for $\mathrm{C}_{3}\text{Fs}/\text{CF}_{3}\mathrm{I}/\text{CO}_{2}$ is most obvious when the content of $\mathrm{C}_{3}\mathrm{F}_{8}$ is about 10%. The research results in this paper provide a theoretical basis for $\mathrm{C}_{3}\mathrm{F}_{8}$ ternary gas mixtures as a potential replacement gas for SF6.