Analysis of Short Circuit Performance of Split-Winding Transformer Using Coupled Field-Circuit Approach

Summary form only given. The split-winding arrangement requires special short circuit design considerations. During short circuit conditions, there is a considerable distortion of the leakage field, which in turn produces high axial short circuit forces. This paper deals with the computation and analysis of electromagnetic forces in windings of split-winding transformers. A nonlinear-transient field-circuit coupled finite element model is used to simulate the split-winding transformer. A 70 MVA, 3-phase, 220/6.9/6.9 kV split-winding transformer is modeled under pre-set and post-set short circuit test conditions. Under the pre-set condition, the transformer is analysed with one as well as both the LV windings short-circuited to compare the axial forces produced in the windings for these two cases. The results show that there is a considerable rise in the axial forces when one winding is short circuited as compared with the case when both windings are short-circuited. The effect of initial magnetization of core on axial short-circuit forces is calculated and discussed. It is also shown that even though post-set method eliminates inrush related problems there is not much respite in short circuit forces.