Calculation and Analysis of Short-circuit Performance of a Split-Winding Transformer with Stabilizing Windings

Abstract

Short-circuit faults are inevitable in split-winding transformers with stabilizing windings, and the resulting transient electromagnetic force may cause detrimental damages to the equipment. Therefore, the short-circuit force is identified as an important issue to be duly addressed in the design stage. This paper focuses on a comprehensive analysis of the characteristics of the split-winding transformer with stabilizing windings under different short-circuit faults. In this regard, a FEM based field-circuit approach is proposed. And a SFFZ10-88000 kVA/220 kV split-winding transformer with stabilizing windings is used as a prototype to investigate its transient performances with both full-crossing and half-crossing conditions under different short-circuit faults. The symmetrical component method is presented to compute the short-circuit currents. A prototype test model is fabricated to verify the correctness of the proposed FEM method. The results reveal that the axial forces exerted on the winding in half-crossing short-circuit faults are generally larger than those in full-crossing short-circuit faults. Moreover, there is a considerable short-circuit force in the stabilizing winding in cases of a single-phase earthed fault and a two-phase earthed fault and there is no current in the stabilizing winding under other short-circuit fault cases.