The relay protection tester is an important test equipment in the power system. It is mainly used for testing all kinds of traditional relays and protective devices. Meanwhile, it is also used for testing modern microcomputer protection. It is particularly worth mentioning, that plays an important role in testing transformer differential protection and spare automatic cutting devices. Specifically, the relay protection tester can test every single component in secondary scheduling, these components include current, voltage, time, difference, balance, negative sequence, distance, power direction, inverse time lag, frequency, synchronous, re-closing, and other relays. In addition, it can also simulate a variety of simple or complex transient, permanent, transition failures for the test of a whole group of drives.