On the basis of analysis on some questions of relay protection in auxiliary power systems

like the imperfection in configuration and the actuation time is too long

a scheme was proposed for relay protection design

such as configuring a specialized main protection for 6kV busbar

adding a time limited current fasttrip protection on the high-voltage side of low-voltage transformers in auxiliary power system

optimizing the cooperation of reserve protections and then designing the configuration of relay protection in auxiliary power system according to the optimizing rule.Taking a 600 MW unit as the example

settings calculation was carried out.The results proved that the configuration of relay protection in auxiliary power system is integrated perfectly due to the optimization

the coverage of protection is reasonable and the actuation time of reserve protection has been remarkably shortened.Thus

the actuation speed and security of the auxiliary power system are promoted.