Main transformer zero-sequence current protection test method

The invention discloses a main transformer zero-sequence current protection test method. The method comprises the following steps of: (1) grounding a single phase of a high-voltage side of a main transformer, and simulating a fault outside a zero-sequence differential region of the main transformer; (2) temporarily reducing a main transformer zero-sequence differential protection action constant value and temporarily reducing a main transformer zero-sequence overcurrent protection constant value; (3) checking the zero sequence CT polarity correctness of the main transformer on a protection device by using the current formed by the residual magnetism of a unit; and (4) rising the current so as to check the zero-sequence over-current protection action of the protection device. According to the test method, whether the polarity of a zero-sequence CT is correct or not is verified by simulating the polarity reverse connection condition of a zero-sequence CT loop and checking the action conditions of zero-sequence differential protection and zero-sequence over-current protection only through one-time current rising operation, the test logic is strict, the result is reliable, operation is easy, external wiring does not need to be changed, the risks of CT open circuit and wrong wiring do not exist, the life safety of workers is ensured, and a unit starting test is smoothly carried out.