Experimental Analysis of Degradation in Insulation Performance After Arc-Preconditioning in High-Voltage Circuit Breaker

In the capacitive current switching duty of high-voltage circuit breakers, arc-preconditioning has been standardized to check insulation performance after short-circuit current interruption. Therefore, it is necessary to consider the degradation in insulation performance due to the wear of electrodes and insulators caused by arc-preconditioning. Since insulation performance depends on the electric field and gas density, we evaluated the effects of gas flow and electric field on the stroke position for a product-sized model circuit breaker through fluid and electric field analyses. The impact of arc-preconditioning on insulation performance was analyzed from the breakdown voltage changes before and after arc-preconditioning. The gas density in the high electric field at the tip of the electrode depends on the stroke position, and the electron behavior emitted from the electrode changes with the polarity of the applied voltage. The effects of stroke position and arc-preconditioning on dielectric breakdown performance were systematically evaluated by analyzing a breakdown model that takes into account electron propagation from the electrode tip and changes in breakdown voltage before and after arc-preconditioning. It was found that the degradation in electrodes and insulators due to arc-preconditioning does not uniformly degrade insulation performance, but the degradation effect differs depending on the stroke position, such as when the breakdown voltage does not change.