Study of dielectric breakdown properties in 50%SF₆-50%CF₄ mixtures at 1 atm

The reduced critical electric field strength is an important indicator for the evaluation of dielectric breakdown of SF₆ and its mixtures. The electron energy distribution function, reduced ionization coefficient and attachment coefficient of SF₆-CF₄ mixtures were obtained at 1atm and gas temperatures to 3000 K, by two-term Boltzmann equation analysis. Then the reduced critical electric field strength could be determined. The results show that, at temperature above 1800 K, the reduced critical electric field strength of 50% SF₆-50% CF₄ mixture is higher than SF₆ gas; at temperature beyond 2600 K, different from the cases in pure SF₆ and SF₆-N₂ mixtures, due to the dissociation of CF₄, the reduced critical electric field strength of 50%SF₆-50%CF₄ mixture increases with the temperature rising. In order to validate the calculation method and parameters, the reduced effective ionization coefficient and reduced critical electric field strength of SF₆-CF₄ mixtures under ambient temperature and 1 atm were calculated and compared with other literatures. The comparison results confirmed the validity of the presented calculation method and parameters.