Computations on the Thermal Characteristics of SF₆ and CO₂ Switching Arcs on a Microscopic Scale

Pure sulfur hexafluoride is a colorless, odorless, non-toxic, inflammable, chemically inert and thermally stable gas and has proven its worth as an excellent interruption and dielectric medium. SF₆ has been successfully used for interruption and insulation purposes as interrupters and circuit-breakers in gas-insulated substations. Due to its long lifetime and high global warming potential, this gas was put on the list of fluorinated greenhouse gases in the Kyoto Protocol aimed at controlling the emission of man-made greenhouse gases. This factor makes the search for an environmentally friendly alternative to SF₆ all the more urgent. In this paper, we conducted computations on the thermal and aerodynamic behaviors of SF₆ and an alternative CO₂ switching arcs in a self-blast chamber in order to compare the switching phenomena and the thermal reignition from an engineering point of view. Through the complete work, the 3,000 K isotherm of the remnant arc column within microseconds after a current zero was used to evaluate the thermal reignition of SF₆ and CO₂ switching arcs with the slope of the tangential line of the transient recovery voltage on a microscopic scale.