Short-Circuit Forces Analysis of Transformers Based on Finite Element Method for Digital Twins

The ability to withstand short-circuit forces is one of key performances of transformers. Finite element method(FEM) is an important means to calculate the short-circuit forces of transformers and is also the core technical support for digital twins. This paper uses the FEM technology to analyze effects of two-dimensional/three-dimensional models, different boundary conditions, and magnetic permeability settings on transformers' short circuit forces. Two-dimensional models were used to analyze the influence of parallel or vertical sections to core window on radial and axial short-circuit forces. The results showed that radial forces acting on the transformer windings along the circumference were similar. But the axial forces differed significantly. Three dimensional models were used to analyze the influence of magnetic permeability of materials such as iron cores, tanks, and magnetic shielding on leakage magnetic distribution and short-circuit forces. The results showed that setting nonlinear magnetic permeability of tanks can make the calculation more accurate. Via the simulations, suggestions for calculating transformers' short-circuit forces were proposed, which can effectively guide the design of a transformer's short-circuit capacity.