Quasi-Three-Dimensional Computations of the Microscopic Thermal and Dielectric Characteristics of an SF₆ Rotating Switching Arc

Pure sulfur hexafluoride (SF₆) is chemically inert, non-flammable, non-toxic and thermally stable, and it has excellent dielectric strength and arc-quenching and control properties. The switching-off process of SF₆ arc discharges occurs at the region between the contacts during the opening sequence to interrupt the flow of excessive current in a faulty network. The arc is tolerated in a controlled manner until a natural current zero when the arc discharge is rapidly quenched to restrict the thermal and dielectric reignition to the interruption. An SF₆ self-blast switching chamber combines two advantages of blowing by heat expansion of the SF₆ and arc rotation by electromagnetic effect of coil to improve the switching performance on thermal and dielectric reignition. The thermal and aerodynamic behaviors of an SF₆ rotating switching arc in the chamber physically are complex and difficult to understand only by measurement due to their three-dimensional effects. Since the late nineteen-eighties, significant progress has been made in the method of computational fluid dynamics describing the physical processes occurring in the switching arc. The final goal of computer simulation technology on the arc switching is to predict the switching phenomena on the thermal and dielectric reignition from an engineering point of view. In this paper, we have conducted quasi-three dimensional computations to predict the thermal and dielectric reignition of SF₆ rotating arcs occurring after a current zero in the self-blast switching chamber. Through the complete work, the microscopic thermal and aerodynamic behaviors of the remnant arc column after a current zero should be good criteria to predict the thermal and dielectric reignition of the rotating switching arc in the chamber.