Study on Mitigation of OCR Malfunction Due to SFCL in Power Distribution System With DER

초록

The superconducting fault current limiter (SFCL) is an effective device to mitigate the fault currents with minimal power loss and negligible impact on the power distribution system. However, the SFCL can cause the malfunctions in existing overcurrent relays (OCRs) and disrupt the protection coordination. This paper presents an impedance-based compensation method for OCRs in a power distribution system with distributed energy resource (DER). DER is simply modeled as ideal three-phase voltage sources behind internal impedances. DER affects OCR operation by supplying additional fault current and the operating characteristics of OCRs located near DER is altered by the SFCL. The impedance-based compensation method compensates OCR malfunctions and restores the protection coordination between OCRs. To validate the effectiveness of the proposed method, fault simulations involving unbalanced ground fault were performed using PSCAD/EMTDC.

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