Analysis of the Effects of Capacitances on Transformers in Transient Regimes by Finite Element Method

High currents occurring in transformers in transient state may cause the insulation materials to deteriorate. In this paper, the effects of the capacitance values between the winding and the core and between the windings on the transition of the lightning strike applied to the secondary side to the primary side of power transformers were analyzed. Transformer models were created in ANSYS@Maxwell-2D environment, which realizes a solution based on Finite Element Method (FEM). In simulation studies, a lightning impulse voltage of 1/100 µ s was applied to the secondary side of the transformer with a special method. It has been observed that the change of the values of the capacitances between the windings in power transformers affects the amplitude of the primary lightning impulse voltage. With this study, the weak points of the insulation materials of transformers windings were determined and the electric field distribution was analyzed.