Study on Improvement of Protection Coordination Between OCR and UVR Due to SFCL’s Application in Power Distribution System with Induction Generator; [유도발전기가 연계된 배전계통에 초전도한류기 적용에 따른 OCR UVR 과 간 보호협조 개선에 관한 연구]

초록

In South Korea's power distribution system, where 154 kV substations supply multiple feeders, faults on one feeder can cause voltage drops across other feeders on the same bus. These voltage drops pose significant risks to feeders with sensitive loads, such as semiconductor manufacturing facilities, which are vulnerable to voltage sags, leading to productivity and economic losses. To mitigate these issues, Under Voltage Relays (UVRs) are employed. However, coordinating UVR's operation on sound feeders with Over Current Relay (OCR) on the faulted feeder becomes more complex, especially with the application of Superconducting Fault Current Limiter (SFCL). This paper analyzes the impact of applying SFCL and induction generator (IG) on the operation of OCR and UVR in power distribution system. To address issues of UVR's maloperation and delay of OCR's operation, this study proposes adjustments to the pickup values of both relays. The results show that increasing the UVR's pickup value prevents maloperation, while lowering the OCR's pickup value reduces operation delay, improving the protection coordination between protection relays. Notably, with both SFCL and IG applied, the OCR's pickup value can be set even lower, enabling faster fault clearance. This study presents an approach for protecting sensitive loads by properly adjusting the UVR's settings on feeders vulnerable to voltage sags, thereby facilitating rapid system's recovery. Copyright © The Korean Institute of Electrical Engineers.

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