A Novel Superconducting Current Limiting Type SF6 Gas DC Circuit Breaker Assisted by Quenching Voltage

Abstract

This paper proposes a novel superconducting current limiting type SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> DC circuit breaker (DCCB) which has bi-directional breaking function, and the commutation capacitor of the DCCB is charged by quenching voltage of superconducting coils. The new DCCB combines a mechanical type DCCB and superconducting coils. When a short-circuit fault occurs, the superconducting coils quench automatically and become a large quenching resistance. The commutation capacitor in the mechanical type DCCB is charged by quenching voltage of the superconducting coils, and no extra charging circuit is required. Thus, the charging difficulty in high voltage is avoided. Compared with the self-excited oscillation interruption method, a much higher charging voltage and discharge current can be obtained by the quenching voltage of the superconducting coils charging method. Besides, the high discharge current can help the fault current to obtain an artificial current zero immediately. The working and interrupting principles of the novel DCCB are investigated by simulations and experiments. Results show that the DCCB can interrupt the normal, overload and short-circuit currents effectively. Arcing time of the short-circuit interruption can be reduced from several milliseconds or longer to only 0.15 ms and the interruption ability is greatly improved by the proposed interrupting principle.