Experimental investigations of the quality of power system small-scale transformer modeling

The paper presents problems with experimental verification of the quality of small scale transformer model which is aimed to describe its “harmonics” properties in the kHz frequency range. Two small, three-phase power transformers (220/380V, 5 kVA) were fully accessible for experimental observations (primary and secondary side voltages and currents) with the use of the low cost, low voltage isolating/conditioning circuits. As they are not the operating power system transformers, they could be extracted from the grid and their frequency properties were relatively easily experimentally investigated in energized and deenergized states. That way relatively full knowledge on transformers properties was collected, what allowed for use the correctly parameterized transformer model in the laboratory/university subgrid modeling. The accuracy of the grid model in different load configurations was used for verifying the correctness of the transformer model. In the paper only single phase connections of transformer are discussed. Interesting data on their three phase behavior were collected but are not presented here due lack of space and its not too clear current physical explanation.