A New Transformer Model Based on Modified Multi-Conductor Transmission Line Theory

To calculate the very fast transient overvoltages in transformer windings, a model based on the modified multi-conductor transmission line (MTL) theory is proposed in this paper. In original MTL model, the lengths of all the conductors are considered to be equal and this approximation can cause inaccuracy. In fact, the lengths of the conductors are decreasing from the outside to the interior. This new model can settle this problem. Based on the original transmission line model, equations of curve-shaped MTL are deduced. The single-input and multi-output model of the modified transmission line model of the transformer is obtained in this paper and is used to calculate the voltage distribution of the winding. Some measurements are conducted to verify the calculation results. And comparisons between the original MTL model and the modified model are used to illustrate the deviations.