Flexible DC distribution network has become an important part of future distribution network because of its many advantages. DC circuit breakers are important equipment in constructing flexible DC distribution network

whereas

the overvoltage generated during the operation of DC circuit breaker endangers the insulation safety of the system. This paper establishes a ±10 kV three-terminal flexible DC distribution network in the Pscad/Emtdc platform

and carries out theoretical and simulation analysis of the breaking strategy and operating overvoltage of mechanical DC circuit breakers in the case of interrupting bipolar short-circuit fault on the cable side

bipolar short-circuit fault at the outlet of current-limiting reactor

and single-pole ground fault. Furthermore

the influence of operating timing sequence of mechanical DC circuit breakers at both ends of the line on operating overvoltage is investigated. Finally

the analysis results are summarized and the research in present work provides a reference for the protection strategy and insulation coordination of the flexible DC distribution network.