A current-slope based fault detector for digital relays

Any reliable transmission line protection scheme is expected to quickly detect faults on lines to initiate the procedures for fault section identification and fault classification. This paper proposes a new fault detection technique for digital relaying of transmission lines in power systems. The three sampled phase currents at the relay point are processed by the proposed current-slope based method to detect faults. The performance of the proposed algorithm is evaluated by considering frequency deviations, sudden load changes and other practical situations. Results indicate that the algorithm is very fast and accurate compared to other methods.