An Analytical Method for the Analysis of Transformer Windings Having Non-Uniform Capacitance Distribution

Abstract

A direct procedure for the transient and frequency analysis of transformer windings with location-dependent inter-turn capacitance distribution is presented. This can help simulate windings with non-uniform insulation. The derived analytic solutions in the Laplace domain are based on expressing the non-uniformly-distributed series capacitance per unit length as the sum of a constant term and a variable part proportional to the square of the distance from the winding’s source terminal. The closed-form solution can yield the voltage and current distributions along the winding, as well as its input impedance. The latter can be used in order to identify the resonance frequencies. The analyses take the winding’s losses into consideration. Different degrees of capacitance non-uniformity as well as various neutral point treatments are investigated. The suggested approach is validated by its application to special cases and to examples for which solutions are available elsewhere.

Keywords: Power transformers, winding, modeling, equivalent circuit, distributed parameter circuits, non-uniform, frequency response, resonance