semiconductor element 30 a fast switch 40 first and second power fuses 50 and 60 a current limiting resistance element 70 and an scr silicon controlled rectifier 80 the power semiconductor element 30 and the fast switch 40 are connected in series to form a main circuit a serial connection between the scr 80 and the first power fuse 50 is connected in parallel to a serial connection between the power semiconductor element 30 and the fast switch 40 and a serial connection between the current limiting resistance element 70 and the second power fuse 60 is connected in series to the first power fuse 50 these connections of the scr 80 the first and second power fuses 50 and 60 and the current limiting resistance element 70 form the current limiting circuit the measurement unit 10 measures a current and current accruement the measurement unit 10 preferably includes a ct current transformer and a rogowski coil the ct and the rogowski coil are well known in the art such that no more explanation thereto will be provided herein and omitted in a case where the measurement unit 10 measures a current accruement to detect a failure that is in a case where a fault current is introduced the ffd 20 transmits a turn on signal turning on the scr 80 to the scr 80 transmits an open signal opening the fast switch 40 to the fast switch 40 and transmits a turn off signal turning.