A frequency dependent model for Δ-Y0 coupled distribution transformers

The paper describes some of the investigations made in order to evaluate the possibilities for defining a model valid for a class of distribution transformers (10/0.4 kV) covering the frequency range from the operational frequency to above the most dominating disturbing frequencies. The work reported covers both an analytical description of the semi-ideal Δ-Y₀ coupled transformer; measurements in the lab giving the nodal admittance matrix for a 400 kVA transformer; the development of an EMTP96 model for the transformer; some transfer-functions for the very same transformer giving a possibility to test the model, and, finally, the results of measurements made on a group of "identical" 100 kVA transformers, i.e. transformers from the same batch are presented. It is shown that it will be possible to use such models with sufficient accuracy for classes of transformers