Different Reasons for Mal Operation of Numeric Relay for 220/400kV Line

Un-interrupt and reliable power supply is very  important issue in Electrical power system .Continuous electric supply in not only need for the large industries but it effects all sphere of life medical facilities ,water supply, education, communication system  etc. There is direct connection between economic growth of nation and power supply. Fault in any of three sectors of power system results in power losses. To ensure reliable various protection schemes are used at generation, transmission and distribution etc. In-spite of modern and sophisticated protection scheme several times power failures are observed .Protection failure are one the main reason that has been witnessed as cause of the power failure. In protection scheme relays are the main components along with other protecting devices. Today numeric relays are most popular device used for the protection of the power system. Still several cases are seen where power system partially or totally collapse. This research paper aims at providing insight to the various reasons which leads to the mal operation of Numeric relay.