Review of Research on Mechanical Direct Current Circuit Breakers

Mechanical direct current circuit breakers with good economic effectiveness and high breaking reliability are one of the main technical routes for fault clearing in DC power grids, and have broad application prospects in DC transmission and distribution systems. According to the difference in breaking principles, the present mechanical DC circuit breakers predominantly involve air type DC circuit breakers, current injection DC circuit breakers, and magnetic coupling DC circuit breakers. This paper provides an overview of three forms of mechanical DC circuit breakers, analyzing the corresponding DC current breaking topology, working principles, and breaking methods, introducing the latest research results of related technologies in terms of the field of MVDC and HVDC current breaking. Air type DC circuit breakers are widely applied to low-voltage DC systems, forcing the current zero through sufficiently high arc voltage generated between the opening contacts and completing the opening, which have the advantages of high working reliability and large short-circuit current breaking capacity. The current injection DC circuit breaker utilizes capacitors or inductors of the transfer branch to generate reverse current, then injecting the reverse current into the mechanical switch and achieving zero crossing and breaking of current, which can be applied into medium voltage DC and high voltage DC systems. Magnetic coupling DC circuit breaker is a novel DC breaking technology, simplifying pre-charging capacitor’s the high voltage charging module by isolating the high and low voltage sides, reducing the costs and increasing the breaking reliability, which also has the relevant research in the medium voltage and high voltage field. This article also elaborates on the key technological development and challenges of mechanical DC circuit breakers, summarizing critical issues of mechanical DC circuit breaker from aspects of establishment of arc mathematical model, improvement of commutation branch, design of energy consuming branch, development of fast operating mechanism, and research on arc extinguishing unit of mechanical switch.