Reliability of Forced Commutation Breaking by DC Vacuum Circuit Breaker

Abstract

In the environment where the forced commutation method of a DC vacuum circuit breaker is adopted to break the large current, the high arc energy in vacuum gap after current zero crossing seriously affects the rapid recovery of the medium strength. In response to such severe breaking conditions, we studied a series of schemes, such as vacuum switch series diode, vacuum switch parallel RC absorption branch, and a vacuum switch series saturation reactor, ao as to increase the vacuum gap "zero rest" time, and reduce the recovery voltage rise rate and plasma concentration after arc. The results of the research indicate that, the reverse blocking effect of the seriesed diode can provide favorable conditions for the recovery of the vacuum medium, but the existence of the RC branch of the diode will cause some leakage current to be injected into the vacuum gap after the current zero crossing, which will affect the recovery process of the vacuum medium; under the diode-free RC branch scheme, the voltage change rate and amplitude of the vacuum switch are greatly improved after secondary zero crossing of the current; adding an absorption branch to the vacuum switch can significantly reduce the rate of change of the recovery voltage; the vacuum switch series saturable reactor can effectively reduce the current change rate by the demagnetization of the saturable reactor near the current zero crossing. The statistical test results show that the vacuum switch series diode, the vacuum switch parallel RC absorption branch, and vacuum switch series saturation reactor can improve the breaking reliability of vacuum circuit breaker to a certain extent.