Traditional mechanical DC breaker interrupts DC circuit by oscillation current superposition method

thus the breaker will bear remarkable forward current when interrupting

increasing damage to the switch contacts of circuit breaker. Considering the shortcomings of traditional DC breaker

we put forward a novel current-source hybrid electromechanical DC circuit breaker. By constructing commutation circuit with power electronic devices

current with controllable magnitude and waveforms can be produced

and positive amplitude of the current is reduced while a current zero is produced. It can effectively reduce the generated arc when HVDC circuit breaker opens

and reduce damage to DC switch contacts to extend its lifetime. DC circuit breaker can effectively switch off rated current and fault current

and it is verified by MATLAB/Simulink simulation software. Moreover

the condition of DC breaker used as metallic return transfer breaker interrupting DC line fault current is simulated with PSCAD/ETMDC. The Mengxi UHVDC project is simulated with PSCAD/ETMDC

and the simulated results validate that the proposed new DC breaker can interrupt the DC line fault current efficiently

and can be used as backup protection of unipolar blocking.