Protection coordination of over current relays in distribution system with DG and superconducting fault current limiter

This paper proposes the use of Superconducting fault current limiter (SFCL), in conjunction with directional over current relays (OCRs) to solve the protection coordination problem in distribution systems equipped with distributed Generator (DG). The SFCL size and optimal directional OCR settings are determined in the grid connected mode. The proposed approach is tested on the IEEE 34 node distribution system in which 26 OCRs are placed. On the occurrence of fault, level of fault current changes which in turn changes the operating time of various OCRs. Therefore, it is important to calculate and suggest method of the relay setting in order to minimize the operating time of relays and also to avoid the mal-operation. SFCL reduces the magnitude of short circuit current on the occurrence of fault and ultimately retains the coordination among various directional over current relays.