GROUND FAULT DETECTING APPARATUS

PROBLEM TO BE SOLVED: To identify a ground fault position without an interruption of the power supply to control circuits when a ground fault occurs in a plurality of control circuits. SOLUTION: A power supply circuit structure comprises a first power supply dividing means which divides and branches out an original power supply in order to supply powers from a DC control power supply 1 to a plurality of control circuits 6 in a control board, second power supply dividing means 5 which subdivide and branch out the secondary side branches of the first power supply dividing means, a ground fault relay 7 which operates when a ground fault occurs, and a ground fault detector 10 which detects a ground current from a load feeder on the secondary side of the second power supply dividing means. A third power supply dividing means 12 which supplies powers from the original power supply to the plurality of control circuits via separated routes is provided and, further, power supply changing means 13 which subdivide and branch out the secondary side branches of the third power supply dividing means via separated circuits are provided.