Analysis of the insulation characteristics of CF₃I mixtures with CF₄, CO₂, N₂, O₂ and air

This paper investigates the insulation characteristics of CF₃I mixtures with CF₄, CO₂, N₂, O₂ and air by Boltzmann equation analysis (with mole percentages), neglecting the influence of electron-vibrational superelastic collisions. The critical reduced electric field strength (E/N)_cr of a electronegative gas can be considered as the value for which the reduced effective ionization coefficient ( - η)/N = 0. First, the reduced ionization coefficient /N, reduced attachment coefficient η/N and (-η)/N of CF₃I mixtures with CF₄, CO₂, N₂, O₂ and air are calculated. Then the (E/N)_cr of those mixtures are determined. The results indicate that CF₃I-N₂ and CF₃I-air have a superior insulation performance than the other three mixtures. Further, the (E/N)_cr of CF₃I-N₂ and CF₃I-air are obviously higher than that of SF₆-N₂ at the CF ₃I concentration higher than 65%, and even higher than that of pure SF₆ at the CF₃I concentration higher than 70%. In addition, the calculated results of CF₃I and CF₃I-N ₂ are compared with the experiment values from other literature for confirming the validity of present calculation method and parameters.