Abstract:Electric arc protection is gradually applied to buses in voltage levels of 35kV and below. In order to improve the reliability, some substations in Liupanshui Power Supply Bureau adopt the double criterion of "arc light and secondary current of power supply" and the scheme of installing an arc light protection device for each bus bar. However, there is a dead-time problem in this scheme, when a transformer runs with 35kV or 10kV busbar loads in parallel, if the fault occurs on the second busbar, the arc protection of the first busbar can not operate because the arc light can not be detected, the arc protection of the second busbar can not operate because the current can not be detected, and the fault of the first busbar exists. The same problem. This paper analyzes the problem and discusses the solution of "current or logic". The arc protection device collects the secondary current of the current transformer of the incoming power supply circuit breaker and the sectional circuit breaker at the same time. As long as any current meets the arc protection current criterion, the arc light also meets the requirements, the arc light protection can move.