Transient Current Interruption Characteristics of a Novel Mechanical DC Circuit Breaker

With the rapid development of multiterminal direct current (MTDC) grids, high-voltage direct current circuit breakers (HV-DCCB) capable of interrupting currents within 5 ms are in urgent demand. The mechanical DCCB has always been one of the main proposals for HV-DCCBs. The current commutation is the prerequisite for mechanical DCCBs to interrupt currents successfully. Focused on the current commutation difficulty, a novel mechanical DCCB has been investigated in this paper. A simulation model of the novel mechanical DCCB in MTDC system for fault current interruption was established in PSCAD. By analyzing the simulation results, the detailed transient varying patterns of current, voltage, and energy in the novel mechanical DCCB during its interruption process are revealed. To verify the feasibility of the novel mechanical DCCB, a prototype was developed in the lab, and current interruption tests were carried out on the prototype. Experimental results have shown that a current of 5.3 kA can be interrupted by the prototype within 3 ms. In the end, failures that occurred in initial experiments are discussed and relative protection measures have been proposed. By adopting these measures, failures are successfully avoided and the normal operation of the novel mechanical DCCB are ensured.