A new microprocessor-based relay for transmission line protection

The authors describe the design and implementation of a novel microprocessor-based relay for transmission line protection. The design incorporates two digital relaying techniques which operate in parallel. Their outputs are fed to a voter logic which is programmed to achieve a high level of dependability. The performance of the relay was evaluated using fault data generated by the Electro-Magnetic Transient Program. The results of the tests show that the proposed relay provides reasonable outputs for all types of fault. The profile of the trip counter also shows that the relay performs satisfactorily. With a threshold of five, the voter logic module issued a trip command in less than one cycle