Kinetic Study of a Decaying SF₆ Arc Plasma in The Presence of Impurities

Abstract

A kinetics model has been developed to study the chemical composition of a decaying SF₆ arc plasma in the presence of impurities such as copper, carbon and water, proceeding from electrode and nozzle erosion or desorption in real SF₆ circuit-breakers. The model is based on the following main assumptions: the plasma is in thermal equilibrium (only one temperature for all the species); the plasma is homogeneous; the pressure remains constant during the decay; the transient temperature evolution is previously imposed. Experimental gas analysis by chromatography, after arcing in a circuit-breaker has confirmed the main results of the calculation: proportion of SOF₂ is much more important than that of SO₂F₂ and very low formation of S₂F₁₀ molecules.