the system can realize continuous on-line monitoring of core grounding current to prevent and deal with accidents earlier. by monitoring the size of the grounding current of the core in operation, the system automatically judges the ungrounding or multi-point grounding of the transformer core to prevent a series of faults caused by the suspension potential and local overheating of the core, and ensure the safe operation of the power transformer. more importantly, it can provide a reliable data basis for the condition maintenance of such equipment.