Modelling multi-limb transformers with an electromagnetic transient program

A generalised formulation of the non-linear behaviour of three-phase multi-limb transformers for use with an electromagnetic transient program is presented. The formulation utilizes direct analysis of a magnetic equivalent circuit to provide a Norton equivalent electrical interface at the transformer terminals. The magnetic equivalent circuit is constructed from a finite number of branches incorporating individual magnetic characteristics and windings. The proposed model is used to compare the operation of a three-phase bank of single-phase transformers and a three-limb three-phase transformer under transient conditions.