With the wide application of microcomputer relay protection

more and more attention has been paid to electromagnetic interference of relay protection device and secondary circuit.This paper takes the case of misoperation of microcomputer protection device of 500 kV booster station in a power plant in Hunan

which is affected by electromagnetic interference

and discusses the formation and characteristics of disturbance source and the route of its propagation to the secondary loop.In addition

the paper proposes specific treatment suggestions and measures to prevent electromagnetic interference based on the actual situation.It is expected to provide reference for optimization design and safe operation on site.