Two-port wideband models of a single-phase distribution transformer with center-tapped secondary

This paper proposes a pair of two-port wideband models for a 10 kVA 7.967 kV/240-120 V single-phase transformer with center-tapped secondary used in distribution lines in Brazil. The models are valid from 10 Hz to few MHz and are derived from measurements of the admittance matrix and the voltage ratio between the high-voltage and low-voltage transformer terminals. Two different conditions are assumed for deriving the models for the transformer. One assumes that one of the low-voltage terminals is short-circuited, while the other assumes that the same terminal is left open-circuited. Both models are validated by means of comparisons with experimental data. It is shown that voltages transferred from the high-voltage side to the low-voltage side of the transformer reach higher amplitudes for the condition where one of the low-voltage terminals is left open-circuited.