Simulation of the formation and propagation of streamers in SF6and its gas mixtures in uniform and nonuniform fields

The formation and propagation of streamers in SF₆ and its gas mixtures were simulated using the hybrid Monte-Carlo-collision / fluid model in uniform and nonuniform fields. The simulation in uniform field is based on accurate numerical solution of Poisson´s equation in conjunction with the continuity equations for electrons, negative and positive ions. Some simplifications for the nonuniform field´s calculation were applied due to the limit of a computer´s calculation speed. The effect of O₂ upon the SF₆/N₂/O₂ gas mixture´s critical field is also discussed. The electron density, positive and negative ion densities, electric field in the discharge channel, which are very important to understand the phenomena of streamer development and to assess the insulation strength of the gas mixture, are also presented in This work.