REDUCED ORDER MODEL FOR TRANSFORMER TRANSIENTS

A complete model for transformers is derived on the base of very efficiently calculated elementary (turn-to-turn) parameters. A high-order turn-to-turn model is constructed for the windings. This model is reduced to a lower order by operating on the resulting matrices. An electric equivalent circuit for the core is obtained from the principle of duality. By the use of test turns the winding model is interfaced with the iron-core. For validation, the frequency response of the model has been compared with test results. The model for the calculation of transients has the form of a Norton equivalent circuit and it can easily be incorporated in a power system transients program such as the EMTP. Examples of calculated transients are given for illustration and further validation.