Insulated condition detector with fault detection and location

An insulated condition detector for detecting an insulated condition of a DC power source insulated from a ground potential portion according to a charge voltage of a flying capacitor charged with a charge amount corresponding to a voltage of the DC power source and a charge voltage of the flying capacitor through an insulation resistance measuring circuit of the DC power source including an insulation resistance of the DC power source, the insulated condition detector comprising:

• a peak holder being selectively connected to a discharger of the flying capacitor at the start of discharge of the flying capacitor and configured to charge a hold capacitor with potential corresponding to a peak value of a discharge voltage of the flying capacitor and hold the potential;
• a hold value measuring unit configured to measure the potential held in the peak holder after the start of discharge of the flying capacitor and in a state that the peak holder is electrically isolated from the discharger;
• a charge voltage detector configured to detect a charge voltage of the flying capacitor according to the value measured by the hold value measuring unit;
• a test charger configured to charge the hold capacitor with predetermined potential in the electrically insulated state from the discharger if the potential held in the peak holder and measured by the hold value measuring unit is zero;
• a test measuring unit configured to measure a charge voltage of the hold capacitor after the charging by the test charging unit;
• and
• a fault detector configured to detect a fault location according to the values measured by the hold value measuring unit and test measuring unit.