Experimental Considerations for the Dielectric Characteristics of Inhomogeneous High Temperature SF₆ Gas in a Gas Circuit Breaker

Abstract

The purpose of the present paper is to show the dielectric characteristics of inhomogeneous hot SF₆ gas in a dead-tank-type gas circuit breaker (GCB) experimentally. High-temperature and low-density SF₆ gas generated during a heavy current interruption is distributed inhomogeneously in the grounded tank, and can strongly threaten the dielectric capability of the GCB. Few studies, however, have been carried out on the dielectric characteristics of the inhomogeneous hot gas. Using small gap discharges, the hot gas behavior of a GCB model, having breakdown or no breakdown occurring, was investigated. As a result, it was found that there was little or no effect on breakdown voltages of the cool gas in the breakdown paths. This suggests that the breakdown voltage of inhomogeneous hot gas could be obtained as the applied voltage at which the electrical field strength equals E_crit of local hot gas at the concerned location.