Numerical and Experimental Investigations on Transformer Winding Damages Under Multiple Short-Circuit Faults

Damages of transformer windings caused by short-circuit (SC) faults have long been an issue of concern. In this paper, a numerical method on the basis of electromagnetic-mechanical (E-M) coupling analysis is presented. Considering the nonlinear stress-strain relations of copper conductors and insulation spacers, winding mechanical behaviors are simulated under multiple SC faults by implementing the finite element method (FEM) in ANSYS. Furthermore, an actual full-scale 110 kV transformer is subjected to actual SC faults. Due to initial deformations in the winding, significant distortion occurred in the B-phase winding after five SC fault tests. Numerically simulated results and on-site experimental evidences indicate that once the winding undergoes slight deformation, the impact of SC currents will create a significant imbalance in stress distribution, and the increased stress in the fault areas exacerbates the deformation of the winding under multiple SC faults. These intensified effects could ultimately lead to damage or collapse of the winding during multiple SC fault events.