CONNECTION DIAGNOSTIC DEVICE FOR GROUND FAULT DETECTOR

A connection diagnostic apparatus for a ground fault detector including an oscillator connected via a coupling capacitor to an electric circuit with a first connection line and a second connection line, and a voltage detector for detecting a voltage value between the oscillator and the coupling capacitor is provided with a first relay and a second relay provided in the first connection line and the second connection line, and a programmable controller. The programmable controller determines a connected state of the ground fault detector based on a change amount of a voltage value detected by the voltage detector when the first relay is turned on or off and determines the connected state of the ground fault detector based on a change amount of a voltage value detected by the voltage detector when the second relay is turned on or off.