Simulation Study on the Influence of Different Short Circuit and Ground Fault on Transformer Winding State Under the Coupling of Multiple Physical Fields

A three-dimensional simulation model of three-phase transformer is built based on the theory of electrical, magnetic, thermal and mechanical fields to study the influences of different short circuit and grounding faults on the winding state of transformer after multiple shocks. By considering the influence of temperature on the winding material properties, a bidirectional couple simulation of electromagnetic and thermal field is established. The electrical, magnetic, thermal and other physical quantities under each fault type are introduced into the transient structure field, and the winding deformation is calculated. The results show that when the three-phase short circuit on low-voltage side occurs, the flux leakage density inside the transformer reaches the maximum. The disc in the middle of the winding obeys the overall magnetic density distribution, and the rest of the disc is large at one side, while it is small at the other end. Furthermore, when the three-phase short circuit on low-voltage side occurs, the winding temperature reaches up to the highest, and the highest temperature is 97.36 ℃, which is located at 0° of phase A low-voltage winding. Moreover, when a single three-phase short circuit shock occurs at the low-voltage side, the displacement reaches the maximum, which occurs in the range of −20° to 20° and 1/3 to 2/3 height of the high-voltage winding. The maximum cumulative displacement of the winding reaches the maximum after multiple two-phase grounding shocks at the low-voltage side, and the cumulative displacement increases with the increase of the number of shocks until it tends to saturation. The research provides a reference for the multiple physical field coupling numerical simulation of transformer. © 2023 Science Press. All rights reserved.