Negligible Effect of Negative Ions on the Constriction of Arcs in SF6

Abstract
From material functions calculated with and without the presence of negative ions, temperature profiles have been calculated for arcs in sulfur hexafluoride. Account is taken of the influence of the negative ions on both the electrical conductivity and the radiation emission coefficient. Results indicate that negative ions have a negligible effect on arc temperature profiles, it being assumed that local thermal equilibrium exists. The constricted arc profiles that are obtained at low currents are due to the reactive peak in the thermal conductivity.