Nonlinear Frequency Dependent Transformer Model for Electromagnetic Transient Studies in Power Systems

Transformer models for system studies derived without taking into account the frequency dependency of its magnetizing branch are not adequate for representing the transformer performance over a wide range of frequencies and operating conditions. This paper describes a procedure for taking into account the frequency dependent characteristics of the transformer based on an analysis of the electromagnetic field distribution within the laminations of the transformer core. A one dimension linear diffusion problem is analyzed. A simple linear equivalent circuit of the Norton type is synthetized. This circuit is an exact representation of the transformer at any frequency and for any type of excitation.