Voltage and current performance of a three-phase transformer under unbalanced voltage supply

Abstract

This paper presents an analysis of the voltage unbalance effects in a three-phase transformer for voltage and currents in the secondary side when an unbalanced voltage appears in the primary side. Theory about the voltage unbalance characterization and the unbalance factors is presented. Also, a description of the three-phase transformer selected for the research is showed, together with its model and the equivalent circuit used in the simulations. Clear linear trends are observed between the voltage and current unbalance factors of the primary and secondary side of the transformer, which allows to estimate the performance of the transformer under different voltage unbalance cases. A certain voltage unbalance in the primary side produces an unbalance of voltages and currents in the secondary side, regardless the load index of the transformer.