Highlighted Technical Issues Concerning Test Technologies of HV DCCBs

Direct current circuit-breakers (DCCBs) are evolving rapidly. Guide for testing DCCBs is under development where issues relevant to test criteria, testing method and test set-up inspired meaningful discussions. We raise examples of three latest topics in this paper. (1) Reignitions and restrikes in AC CBs can generate over-voltages, threatening other components in the power system but differently, these phenomenon inner a mechanical DCCB has no impact on the system. Nonetheless, they will result in higher peak interrupted current and prolonged current breaking time, which means more energy stress to the MOSAs. (2) MOSAs get in the way of conducting insulation tests because these elements can interfere with the applied test voltages. One way to overcome this obstacle and meanwhile to maintain the voltage shared among components inside the tested DCCB is replacing MOSAs with insulating material. (3) A full-scale test on extra high voltage and above DCCBs requires an extremely large amount of energy which can be practically unfeasible. In such a case, unit test is an alternative based on strict rules.