Saturation characteristics of a transformer under DC bias and their influence on the distribution of DC current in an AC power grid

Abstract

Based on the phenomenon of direct current (DC) component occurring in transformer magnetizing current in the case of transformer saturation resulting from DC bias, the influence of such a DC component on the distribution of DC current in the transformer neutral point is analyzed. By virtue of PSCAD/EMTDC software, the simulation model of a transformer suffering due to DC bias is built up to analyze the DC current characteristics in the transformer neutral point in the cases of taking into account and taking not into account of the transformer saturation caused by DC bias, respectively. According to the results obtained, the simulation value of DC current in the Yichang‐region power grid taking no account of transformer saturation is corrected. It is verified that the saturation of transformer magnetizing branch contributes to increase the DC current in the transformer neutral point. Taking into account the transformer saturation influence, the prediction accuracy of the DC current distribution in the AC power grid can be improved. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.