DC circuit faults caused by AC interference may cause the misoperation of relay protection devices

which threatens the safety and stability of the system. To solve this problem

a new type of AC interference overvoltage protection device is developed. The device sets the AC withstand voltage by adjusting the access quantity of zinc oxide arresters

and activates LC filter circuit by bridge circuit when AC interference occurs

so as to release AC component safely. The experimental results show that the device can accurately identify AC interference simulation faults of different amplitudes

effectively protect and monitor the DC system of substations

and significantly improve the safety level of power grid operation.