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 ra pidly recombine with electrons, modifying the resistivity of the plasm a. 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 resu lts show that convection acts on S-2 molecules which, at the edge of t he discharge and for temperatures of between 4000 and 6000 K, are over populated with respect to equilibrium. Through charge exchange process es between S-2 and S-2(+) particles, the overpopulation of S-2 leads t o an overpopulation of the S-2(+) ions. These ions mainly recombine wi th electrons, lowering the electron population and modifying the elect rical conductivity of the plasma.