Radial-strength research of transformer windings considering temperature effect under reclosing short-circuit conditions

With the fast capacity growth in power systems, transformer failures caused by short circuits have become the primary problems in maintaining their operation reliabilities. In addition, automatic reclosing will make the transformers suffer multiple short-circuit impacts in a short time interval, therefore challenging the transformers' short-circuit stability. In this study, a comprehensive analysis of radial strength under reclosing short-circuit conditions is carried out on a 50 MVA transformer taking the temperature influences into consideration. First, the power transformer's fault model is established to calculate the short circuit currents under initial short circuit and reclosing conditions. Then, three-dimensional (3D) finite element analyses of the transformers' winding short-circuit forces with initial short circuits and reclosing are conducted. Finally, the temperature influences on the windings after the reclosing are calculated. By taking into account the qualities of the self-adhesive transposition wire with temperature effect, the stress characteristics of the windings are calculated.