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This paper proposes a dc circuit breaker for voltage source converter (VSC) based high voltage dc (HVDC) transmission systems. The dc circuit breaker is a solid-state breaker which consists of many semiconductor devices in series with maintaining equal voltage balancing, making it possible to apply to high voltage applications. Moreover, the surge voltage across the circuit breaker is reduced by employing a freewheeling diode. In a system rated at 300 MW in power and 250 kV in dc voltage, conduction loss of the proposed circuit breaker consisting of 4.5 kV devices is estimated at 0.045% of the rated power, which is enough small comparing to the VSCs' power loss. A downscaled HVDC transmission system model rated at 10 kW in power and 360 V in dc voltage was built and a series of experimental results demonstrate the dc fault clearing and rapid restoration of power transmission.