Restricted earth fault protection with superconducting fault current limiter for 100% stator winding

Abstract

Conventional Restricted earth fault protection provides protection about 80 to 90% of generator stator winding against earth fault when neutral of generator is earthed through a resistance. In this paper, superconducting fault current limiter an innovative device is used along with restricted earth fault protection to provide 100% stator earth fault protection. A specific generator is considered which is provided with restricted earth fault protection to protect 90% of its winding against earth fault. Then a resistive SFCL is applied in the protective scheme replacing the neutral earthed resistance to a lower value than the previous one. It is found that excellent operational characteristics of SFCL facilitate the restricted earth fault relay to operate from very beginning to the end of the generator winding and provide 100% stator earth fault protection.