Development of digital relay for 275 kV AC filters at the Shin-Shinano frequency converter station

With the extension of the 300 MW Stage 2 of the Shin-Shinano frequency converter substation by The Tokyo Electric Power Co., Inc. in 1992, a new digital type of protective relay for the 275 kV harmonic filter system was developed to replace the existing electromagnetic type. New operating algorithms are used with the digital relay, centred on root mean square (RMS) value operations which use high frequency sampling data for detecting faults in the capacitors and reactors from which the harmonic filter system is constructed. An Electromagnetic Transients Program (EMTP) test was used in factory tests. The authors discuss the digital relay operating algorithms which were developed, the equipment configuration, test results, etc