Elastic-plastic deformation analysis of power transformer windings considering cumulative effect

The deformation of windings caused by short circuits is one of the key factors leading to transformer failures. To explore the elastic-plastic deformation law of transformer windings under multiple short-circuit impacts, a SFZ7-31500/110 power transformer is taken as the research object to construct a three-dimensional finite element simulation model of the transformer. Through magnetic field-structure field coupling calculation, the leakage magnetic field distribution of the transformer and the magnitude of the electromotive force on the windings during short circuits are obtained. The deformation characteristics and cumulative effects of windings under multiple short-circuit impacts are systematically analyzed. The results show that under short-circuit impacts, the deformation directions of high- and low-voltage windings are opposite, and the deformation of low-voltage windings is significantly greater than that of high-voltage windings. In addition, due to the influence of the iron core structure, the force and deformation of the same winding located inside and outside the iron core window show significant inhomogeneity, and the deformation of the winding inside the window is larger. As the number of short circuits increased, the plastic strain on the low-voltage windings gradually accumulate. It grows rapidly in the early stage, but the deformation accumulation speed gradually slows down and tends to stabilize due to the material hardening effect. On the contrary, the high-voltage windings maintain elastic deformation throughout the process and does not show plastic deformation. The research results have certain guiding significance for the analysis of the dynamic stability of transformer windings.