Ground fault troubleshooting and non-power-cut core alignment detection method for secondary direct current system of transformer substation

The invention provides a transformer substation secondary direct current system ground fault troubleshooting and non-power-cut core alignment detection method. The method comprises the steps that equivalent capacitance of a to-be-detected cable is obtained; constructing an oscillation detection loop, and taking the equivalent capacitor as a constituent part of the oscillation detection loop; acquiring a detected oscillation frequency; and judging core alignment information or ground fault information according to the change of the oscillation frequency. Core detection and ground fault detection of the direct-current cable are realized by means of the equivalent capacitance parameter of the cable, the equivalent capacitance is obviously changed when the direct-current cable is grounded or core detection is abnormal, and the grounding state or core detection condition of the direct-current cable can be represented by monitoring the equivalent capacitance parameter of the cable. The change of the equivalent capa