Dynamic behaviors of the streamer development and propagation in SF6

SF₆ gas is an important insulated medium and is wildly used in electric power industry for gas-insulated equipment; this paper aims to deeply understand the streamer discharge mechanism in SF6, and to better use of SF₆ gas in the electrical equipment. The two dimensional and self-consistent fluid model of the gas discharge is established based on the electron and ions continuity transfer equations coupled to Poisson´s equation, furthermore including the model of photoionization. To overcome the problem about enormous calculation required of photoionization, some simplified methods are implemented in this paper. In simulation, the particle flux-continuity equations is solved by the flux corrected transport technique (FCT), and the iterative symmetric successive over-relaxation (SOR) method is used to solve the coupling Poisson´s equation. Results of two-dimensional simulation of cylindrically symmetric streamer in SF₆ between parallel-plane electrodes are obtained. We present and discuss conclusions about streamer transport based on the results of these studies. The temporal and spatial transformation of charged particle densities, electric field strength, discharge current and discharge propagation velocity during the progression of discharges are investigated and the results indicated that, the processes of discharge have three phases: avalanche phase, streamer formation phase and streamer propagation phase. In addition, by comparing the results of simulation with and without photoionization process can be seen that the photoionization offers a large number second electron, and is absolutely necessary during the streamer propagation phase, which accelerates the velocity of the streamer propagation.