An expert system to evaluate the operating response of the distance relays during a fault

This paper describes an expert system designed to analyse the response to a short circuit fault, of all the distance protection schemes located within a region of a power network. The expert system identifies which, if any, relays have maloperated, and assesses the response of the distance relays that did not trip correctly. The paper details the different expert system models that were built to locate the faulted feeder and also to evaluate the validity of the relays that responded to the fault. The evaluation includes finding whether any communication channels have failed, and if they have, determine whether the relay failed to send/receive the intertrip/block signals