Enhancement of Protection Coordination Between OCR and UVR in Power Distribution System According to Application of SFCL and Induction Generator

초록

In modern power distribution systems, particularly in South Korea, where 154 kV substations supply multiple feeders, faults on a single feeder can cause voltage drops that affect other feeders connected to the same bus. These voltage drops pose significant risks to feeders with sensitive loads, such as semiconductor fabs, which are vulnerable to voltage sags, resulting in productivity and economic losses. To mitigate these issues, Under Voltage Relay (UVR) is used to protect sensitive loads during faults. However, coordinating the operation of UVR on sound feeders with Over Current Relay (OCR) on the faulted feeder is challenging, especially with the application of Superconducting Fault Current Limiter (SFCL) and Induction Generator (IG). This paper studies on protection coordination enhancement between definite-time UVR and inverse-time OCR in power distribution system according to the application of SFCL and IG. Experimental results showed that applying SFCL and IG can cause OCR's delayed operations and malfunctions in UVR. Therefore, this research adjusted the appropriate pickup values to resolve these issues. The analyses reveal that adjusting pickup values can enhance protection coordination between OCR and UVR. Also the results show that when both SFCL and IG are applied to the faulted feeder, the range of adjustable OCR pickup values is wider than when only SFCL is applied, leading to further improved protection coordination.

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