In order to effectively improve the operation reliability of the current-transferring DC breaker

reduce the complexity of the structure and the control

two diode clamping current-transferring DC breakers are presented for the positive and negative poles. The diode clamping topology changes half of conducting branches of the original breaker to diode branches and adds the bypass switch which is parallel to the conducting switch to improve the protection of the DC circuit breaker under the failure of the ultra-fast mechanical switch. On the premise of ensuring the same DC fault handling capacity

the investment cost is comparable to the current-transferring DC breaker

and less investment cost increment is introduced. A model of a three-terminal monopolar high voltage DC grid is developed in PSCAD/EMTDC to verify the validity of the proposed breaker. Simulation results prove the validity and feasibility of the proposed solution.