Computational analysis of electrical breakdown of SF₆/N₂ mixtures

The main aim of the present paper is to clarify the influence of the SF6 fraction in the SF6/N2 mixture on the breakdown voltage. For this, the two-dimensional axisymmetric fluid model coupled with the comprehensive mechanism of plasma chemical reactions is used. In addition, the influence of various parameters such as the voltage rise time and the SF6 fraction in the mixture is analyzed. It is observed that depending on the voltage rise time an admixture of only 1% of SF6 to N2 results in an increase in the breakdown voltage by 7%–43%. The sensitivity of breakdown voltage decreases with decreasing voltage rise time and is caused by the electron attachment time scale becoming comparable to the breakdown time. The results of simulations confirm that the increase in the SF6 fraction in the mixture leads to an increase in the breakdown voltage. This is explained by the influence of the SF6 fraction on the electron attachment rate coefficients rather than on the ionization reactions.