Cumulative deformation analysis of transformer winding under short-circuit fault using 3-D FEM

It is inevitable for power transformers to suffer multiple impacts of short-circuit (SC) current and huge dynamic electromagnetic force in service which may cause large elastic and plastic deformations. Under the SC fault, the distribution of flux leakage and the amplitude of electromagnetic force may be disturbed by deformations. This paper analyzes the cumulative strain-stress characteristics inner of the transformer windings by using the coupled electromagnetic-structural analysis solution. The dynamic electromagnetic force, mechanical stress, and plastic deformation are calculated by using 3-D finite element method (FEM). An example of two-winding, 110 kV transformer is simulated. It is founded that an initial and little deformation of windings can also influence the distribution of flux density, which may enlarge the electromagnetic force applied in the windings. The cumulative model and results in this paper may be useful to study the prediction of winding deformation state.