Directional Correction of Over-Current Relay using Voltage Slope in Multi Terminal DC System with SFCL

초록

In the DC system, a larger fault current flows due to capacitor discharging than in an AC system. In the event of a fault in the MTDC (multi-terminal DC), although the magnitude of the cur-rent flowing through each DCCB (DC circuit breaker) varies de-pending on the fault location, all capacitors in MTDC may dis-charge and all DCCB may interrupt. In this paper, the trigger type SFCL (superconducting fault current limiter) was con-structed to limit large fault current, and DC OCR (overcurrent relay) was designed to prevent interrupting malfunction accord-ing to the impact of SFCL. When the fault current was small by operation of SFCL, the DCCB did not interrupt or trip time is delayed. These problems cause malfunction even when DC OCR is applied. Therefore, DC OCR requires an additional correction method. In this paper, a new correction method was proposed in consideration of the current direction and voltage slope. The sim-ulation was conducted according to four cases, and the proposed OCR correction was verified to eliminate malfunctions through case studies. CCBY

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