Magnetic-Structural Coupled Simulation of Power Transformer Winding Cumulative Effect

Power transformers play a vital role in electric energy transmission and transformation system. Invisible damage after short-circuit fault is the main cause of transformer instability. Therefore, it is necessary to study the winding cumulative effect of multiple short-circuit impacts. In this work, the electromagnetic and mechanical characteristics of transformer are simulated in a short circuit by coupling magnetic field and structural field. Furthermore, the accumulation of stress and deformation under multiple short-circuit shocks is studied. The results show that the leakage flux of the three-winding transformer during short-circuit fault generally concentrates on the medium and low voltage windings close to the iron core. Under the effect of electromagnetic force, the distribution of winding stress, displacement and plastic strain show that the low-voltage winding is compressed inward and the medium-voltage winding is stretched outward. The middle of the winding is the focus of attention on the short-circuit resistance. Residual stress and winding deformation cause accumulative invisible damage during multiple short-circuit impacts, which will gradually make the transformer stabilization system collapse. This is worthy of attention in the evaluation of the short-circuit stability of the transformer.