Analysis on Protection Coordination of OCRs in Power Distribution System with SFCL

Abstract

As the requirement of the energy increases because the electric power industry has been growing, the fault current becomes higher. Variable countermeasures have been studied to reduce a fault current, since the fault currents influence other devices in a power distribution system. The superconducting fault current limiter (SFCL) is one of the solutions to limit the fault current with no loss in a normal period because the SFCL impedance only occurs during the fault time. However, the SFCL causes the trip delay of the over-current relays (OCR). The trip delay of OCR causes a negative impact on entire power distribution system and maximizes the power burden. In this paper, new OCR’s algorithm using impedance compensation is suggested to solve the operational delay of the OCRs. Algorithm of the OCR consists of all symmetrical impedance components derived from the voltages and currents of the power distribution system to prepare unsymmetrical and symmetrical ground faults. To prove the effectiveness of suggested method, the protection coordination between OCRs according to the SFCL installation was analyzed in 3 types of ground fault. The fault simulations for a power distribution system were carried out by using PSCAD/ EMTDC.