Arc resistance at current zero: a tool to describe the breaking capacity of SF/sub 6/ circuit-breakers at short-line faults

By taking large numbers of voltage and current measurements on SF/sub 6/ high-voltage circuit-breakers in the vicinity of current zero, it is possible to identify a relationship between the resistance of the residual plasma in the arc gap and the maximum rate of current rise that the circuit-breaker was still able to control during short-line fault interruption. This relationship is independent of the geometrical structure of the interrupter unit, and even of the type of circuit breaker tested, at constant fault currents and frequencies. Generally applicable limits are specified for the arc gap resistance that characterize the transitions from thermal to dielectric reignition and from dielectric reignition to withstand values.