PROTECTION SYSTEM FOR DC POWER TRANSMISSION SYSTEM, AC/DC CONVERTER, AND DC POWER TRANSMISSION SYSTEM BREAKING METHOD

An AC circuit breaker 3 is provided between an AC system 1 and an AC-DC converter 5, and a DC circuit breaker 7 is provided between a DC line 6 and the AC-DC converter 5. A bypass switch capable of short-circuiting a converter cell included in the AC-DC converter 5 is connected to the AC-DC converter 5. At the time of a fault in the DC line 6, the bypass switch is turned on to interrupt the supply of DC power from the AC system 1 to the DC line 6.