Device and method for detecting multipoint earthing of voltage transformer for electric system

A device for detecting multipoint earthing of a voltage transformer for an electric system comprises a CPU main controller, an analog-digital conversion circuit and a switch control circuit. A voltage transformer secondary neutral line N600 penetrating into an opening current transformeris connected with a ground point, and output passes through a first filter amplifying circuit to the analog-to-digital conversion circuit. A ground point penetrates through a current transformer to be connected with one end of a sampling resistor Rv, output passes through a second filter amplifying circuit to reach the analog-to-digital conversion circuit, the other end of the sampling resistor Rv is connected with a plurality of branch circuits, and switches and resistors are in series connection with the branch circuits which are correspondingly and externally connected with an A-phase bonding post of the voltage transformer for electricity use. The two ends of the sampling resistor Rv further outputs a 0-5V voltage signal to the analog-to-digital conversion circuit through an isolation amplifying circuit. The invention further relates to a method for detecting multipoint earthing faults of the voltage transformer for the electric system. According to the device for detecting multipoint earthing of the voltage transformer for the electric system and the method for detecting multipoint earthing faults of the voltage transformer for the electric system, whether the multipoint earthing faults of many voltage transformers exist can be accurately detected in time, and the multipoint earthing faults can be specifically located.