Simulation of a decaying SF6 arc plasma:: hydrodynamic and kinetic coupling study

During the decay of a circuit-breaker are, the plasma is subjected to strong blowing which can lead to deviations from chemical equilibrium. The intense convection may therefore be responsible for the presence of cold gas in the hot parts of the plasma. The cold particles then rapidly recombine with electrons, modifying the resistivity of the plasma. In order to study this phenomenon as it appears in circuit-breakers, we made a modelling of the extinction of an SF6 are for a simplified geometry. The two-dimensional model that was set up was followed by a study of the kinetics of SF6 which enabled us to identify the Various reaction processes governing the disappearance of electrons. The results show that convection acts on S-2 molecules which, at the edge of the discharge and for temperatures of between 4000 and 6000 K, are overpopulated with respect to equilibrium. Through charge exchange processes between S-2 and S-2(+) particles, the overpopulation of S-2 leads to an overpopulation of the S-2(+) ions. These ions mainly recombine with electrons, lowering the electron population and modifying the electrical conductivity of the plasma.