Flexible DC power distribution system has become a hot research topic for its advantages such as new energy accessible

etc. Transient current of equipment is the basis of equipment selecting and designing. Theoretical analysis and simulating calculation as well as current limiting measures researches were made to study the transient current’s characteristics of key equipment in a ±10 k V flexible DC power distribution system. Firstly

we analyzed the topological structure of the system

determining the key equipment and their corresponding decisive fault types. Then

we theoretically analyzed

simulated and calculated the transient current. Through simulation

we compared the current limiting effects of different current limiting reactive resistances. Considering the response time of protection

the breaking capacity of DC breaker and economic efficiency as well as spaces

we determined the suitable current limiting reactive resistance series connected in buses of plug-in devices. Finally

we evaluated the transient current level of key equipment. The results show that the transient current level of bridge inductance and sub-modules of main converter is 9.72 k A. The transient current level of two-level VSC converters switched in the line is about 6 k A

and the bus of DC-DC transformers is about 7 k A. The conclusions can be a reference and guidance when designing and selecting key equipment for flexible DC power distribution system.