Computation of static and dynamic axial and radial forces on power transformer windings due to inrush and short circuit currents

In this paper, the radial and axial forces due to inrush and short circuit currents on both inner and outer surfaces of low voltage (LV) and high voltage (HV) windings are calculated. Static and dynamic aspects of these forces which are related to the variation of forces versus winding height and time are analyzed. Power transformer in the start-up mode and under short circuit fault is modeled using two-dimensional (2D) time stepping finite element method (TSFEM). This approach leads to the precise determination of the required signals including current, magnetic flux density, radial and axial forces. Calculated forces are analyzed significantly to compare impacts of the mechanical forces due to inrush and short circuit currents on the windings of the transformer. Three-dimensional (3D) TSFEM is utilized to evaluate aforementioned forces and compare with 2D TSFEM results. In the 3D TSFEM, geometrical and physical characteristics of the all components of the transformer, nonlinearity of the core materials and distribution of the primary and secondary windings are taken into account. 2D TSFEM results are verified by 3D TSFEM results.