Simulation study of transformer cumulative effect under different short-circuit current shocks and prestressing effects

Transformer windings are subjected to repeated short-circuit shocks during the short-circuit process. These repeated shocks can cause cumulative deformation of the windings, eventually leading to insulation failure and winding damage. However, the cumulative effects of these shocks on transformers require further investigation due to variations in short-circuit currents and pre-stress conditions experienced under operating conditions. In this study, the cumulative effects on transformer windings under varying magnitudes of short-circuit currents and pre-stress conditions are analyzed using a finite element model of the transformer. The results show that when -windings are subjected to multiple short-circuit shocks -with different current amplitudes (70%, 80%, 90%, 100%, and 110% of the reference value), the cumulative effects on stress, displacement, and plastic strain become increasingly significant. When the number of shocks exceeds a certain threshold, the stress accumulation in the windings poses a potential threat to structural stability. Additionally, as the amplitude of the short- circuit current increases, the winding stress and displacement exhibit an approximately linear growth trend. Appropriate pre-stressing can mitigate the cumulative effects on the windings to some extent. However, excessive pre-stressing increases the risk of plastic deformation. Among the tested conditions, a pre-stress of 3 MPa -was found to be the most effective in reducing plastic deformation and displacement in the prototype transformer windings. This pre-stress level provides an optimal balance between structural stability and mechanical strength.