Current limiting and recovery characteristics of an AC fast recovery superconducting fault current-limiting breaker

Abstract

With the continuous development of the power grid, the high short-circuit fault current threatens the reliability of the power system. When the short-circuit current is greater than the interrupting capacity of the circuit breaker, the fault current will not be interrupted. Resistive-type superconducting fault current limiter (R-SFCL) has little loss in normal conditions. When a short-circuit fault occurs, R-SFCL can respond within a few milliseconds and limit the fault current. But the recovery time of R-SFCL is too long to satisfy the reclosing demand in the power grid. In this paper, an AC fast recovery superconducting fault current-limiting breaker (FR-SFCB) is proposed. With the operation of a fast switch connected with the superconducting coil, one of the parallel superconducting branches is disconnected, which could provide higher current limiting resistance and decrease the fault current need to be interrupted in fault conditions. Because of the shorter current flowing time, the heat generation and temperature of the advanced disconnected branch are less which can reduce the recovery time significantly. An experimental model is established based on thyristors and superconducting tapes. The effects of prospective current (I p) and the types of superconducting tapes on the current limiting resistance and recovery time of FR-SFCB are investigated. Experimental results show that with the disconnection of the flowing branch, the current limiting resistance of the proposed FR-SFCB increases to more than 3 times of the normal R-SFCL. At the same time, when the FR-SFCB resistance after current limiting is lower than the room temperature resistance, the recovery time of the flowing branch decreases by at least 50%. With access to fast switches, the proposed FR-SFCB can suppress the short-circuit fault current effectively and improve the stability of the power system.