Development of a Chemically Nonequilibrium Model on Decaying SF $_{6}$ Arc Plasmas

This paper describes the development of a 2-D thermofluid model with consideration of chemically nonequilibrium effects self-consistently on an SF₆ arc plasma in decaying phase. The SF₆ arc plasma in decaying phase can be seen in a high-voltage SF₆ gas circuit breaker (CB) during a large current interruption process. The developed model here does not assume chemical equilibrium condition in the arc plasma, although the conventional numerical model often assumes the local thermodynamic equilibrium. This developed model accounts for 19 species, including molecules, atoms, monatomic ions, polyatomic ions, and the electrons. It also takes a total of 122 reactions into account, including dissociation, ionization, and other chemical reactions in SF₆ plasmas. We successfully calculated transient distribution of the temperature and chemical reaction fields for SF₆ arc plasma under a free recovery state for a fundamental study.