Fault component negative-sequence energy direction protection for generators

Fault component negative-sequence direction (FCNSD) relays only need three phases voltages and currents at generator terminals, and can detect various asymmetrical faults in generators with a very high sensitivity. In this paper, the instantaneous negative-sequence symmetrical components, which are based on the Lyon transform an used in the FCNSD relay. From the results of tests on a laboratory generator-transformer unit, it is found that there are very large harmonic constituents in the Lyon component power values. The mechanism of these harmonic constituents is theoretically derived in the paper. To eliminate the influence of the harmonic constituents, a new criteria is proposed-fault component negative-sequence energy direction (FCNSED) protection.