Method for judging single-phase earth fault of controllable high-voltage shunt reactor

The invention relates to a method for judging single-phase earth fault of a controllable high-voltage shunt reactor. The method comprises the following steps: 1) arranging current transformers 1LH and 2LH at the left side and the right side of a low-voltage side earthing point of each phase of the controllable high-voltage shunt reactor respectively; and 2) fetching phase current from the current transformers 1LH and 2LH to form split differential protection for reflecting three-phase ratio restraint of the phase current, wherein the split differential protection is used as main protection for single-phase earth faults of a low-voltage winding of the controllable high-voltage shunt reactor and a hollow reactor, the differential current Iop of the main protection is an absolute value of *1LH+*2LH, and the braking current Ires is equal to 1/2 absolute value of *1LH-*2LH. When any point in the low-voltage winding or the hollow reactor is earthed in single phase, the Iop is equal to total current flowing to the e