Analysis of the insulation characteristics of CF3I gas mixtures with Ar, Xe, He, N2, and CO2using Boltzmann equation method

The present study is devoted to the calculation of electron swarm parameters, including the reduced effective ionization coefficient, electron mean energy, and electron drift velocity, for the gas mixtures of CF 3 I with Ar, Xe, He, N 2 , and CO 2 . These data are computed by employing the Boltzmann equation method with two-term approximation in the condition of steady-state Townsend (SST) discharge. For the purpose of evaluating the insulation strength of CF 3 I gas mixtures, values of the limiting field strength ( E / N ) lim for which the ionization exactly balances the electron attachment are determined from the variation curves of (α − η)/ N . The results indicate that mixtures of CF 3 I–N 2 present the greatest insulation strength among all the combinations for CF 3 I content varied from 20 to 90%. Furthermore, the gas mixture with 70% CF 3 I can achieve a very similar dielectric strength to that of SF 6 . The concerned liquefaction issues are also taken into account to fully assess the possibility of applying CF 3 I gas mixtures in power equipment as an insulation medium.