For round-the-clock and real-time monitoring of the transformer core grounding fault and timely treatment

the current and voltage in the grounding loop of a transformer core under the condition of single point or multi-point grounding were analyzed.A monitoring and current-limiting device was designed based on the principle of on-line monitoring the current in grounding loop

hence the real-time monitoring of grounding current and the automatic control of current-limit resistor were realized.Therefore the current can be limited in the range of standard to prevent the core from overheat or burnout faults.The whole design idea

the function of hardware and software were introduced

and the application condition of this device in the electric substation was also discussed.