Abstract:Relay protection plays an important role in ensuring the safety, high quality and efficient power supply of mine power grid. One of the characteristics is selectivity, which requires that the outage range should be minimized in case of fault. Through the analysis of a power system fault caused by relay protection device override trip, the treatment process is analyzed. This paper summarizes the experience and makes relevant improvements, and discusses the selection of relay protection and the coordination of protection setting between lower end users.