Abstract: Single-phase grounding of a system will change the transient characteristics of the grounding transformer winding, and affect its operating state diagnosis and related protection setting. Since the transient characteristics of the grounding transformer winding are closely related to the overall operating conditions of the distribution network, it is difficult to perform analysis by a single simulation model. Therefore, a multidimensional simulation model composed of the electromagnetic transient model of the distribution network and the multi-physical field model of the grounding transformer is constructed, and the accuracy of the model is verified by test values and actual fault cases. The dynamic power parameters of external systems are input through data coupling, and the physical characteristics of grounding transformer winding before and after single-phase grounding operation are studied. The results show that, when the system is in single-phase grounding operation, the current characteristics of the low-voltage winding of the grounding transformer remain unchanged, the maximum current of the high-voltage winding is increased, the maximum current phase difference is decreased, and the leakage magnetic field shifts outwards and increases the interphase magnetic leakage. The stress deformation law of high voltage winding changes, and the shape variable increases slightly; under the impact of multiple single-phase grounding faults, the winding has no obvious deformation, and the cumulative effect is weak. The maximum temperature rise of the high voltage winding is increased, and the temperature difference between the main winding and phase-shift winding of the same core column is increased.