Fault alarm circuit for detection bridge of DC insulating monitoring device

The utility model relates to an on-line monitoring device for power equipment, especially a fault alarm circuit for the fault monitoring of a detection bridge of a DC insulating monitoring device of a transformer station. The principle of electric current measurement is employed for a DC positive electrode grounding detection bridge and a negative grounding detection bridge, and the circuit is additionally provided with a current sensor and a photoelectric coupler. Through the judgment of a measurement signal of the photoelectric coupler and an induction signal of the current sensor, the integrity of the bridge of the insulating monitoring device of a DC system under the condition that the DC system is grounded. If an open-circuit and short circuit fault happening to a detect bridge is detected, an alarm can be given, thereby guaranteeing the monitoring of the reliability of the DC insulating monitoring device.