Free Recovery of the Gas-Blast Arc Column

The decay of the temperature, velocity, and radius of the extinguished gas-blast arc in SF6 and N2 is theoreticaly investigated. The conservation equations for mass, momentum, and energy in integral form and on the axis describe the decay process. Local thermodynamic equilibrium (LTE) is taken to apply for the determination of the material and transport properties of the gases. The influence of the hot gas mantle on the decay of the arc column is taken into account. It is found that the temperature decay of the column in N2 is much faster than in SF6. Thus the superior dielectric strength of the SF6 column over that of N2 cannot be explained simply by the temperature decay rates. The predicted rate of decay of the column radius in N2 is found to agree well with experimental results. The results of this study are expected to be of value in the determination of the dielectric breakdown characteristics of extinguished arcs.