Power transformers internal insulation design improvements through finite element methods

The knowledge of the potential and field distribution in the insulation system of a transformer, during transient excitation is vital to its construction. This paper deals with insulation design improvements of power transformers using electric field analysis. The calculation methods for electric field analysis inside a power transformer impressed with impulse voltage is presented. Initially, a lumped parameter equivalent model is constructed by dividing transformer windings into several blocks and by computing the electric circuit parameters of this model. Next, the electric field is determined employing the results of the transformer transient model circuit analysis as boundary conditions; a 2D axisymmetrical electric field finite element analysis is performed. Finally a successful application of the proposed method for analysis of a model transformer is demonstrated and the computed results verified against measured results for this model.