Grounded Wye ? Grounded Zigzag Transformer Connection Modelling in Phase Coordinates for Steady-State Studies

ABSTRACT In this paper, an electrical model of a three-phase transformer connected in grounded wye ? grounded zigzag configuration is developed, based in the common core three-phase transformer model as in transformation Banks. The proposed model operates under the phase coordinates scheme in order to simulate operating scenarios with balanced and unbalanced load and perform electrical studies in steady-state in an electrical circuit. The theory basis for the three-phase Transformers electrical modelling is presented and after that, the considered criteria for the suggested model development are shown. Also two ways of characterize the obtained model are presented, one by using an equivalent electrical network and other trough current injection sources, the last one is used to simulate an electrical test circuit via an iterative method which calculates the secondary voltages for three different cases with load variation. The load scenarios analyzed are: Very Low Load (open circuit approach), and balanced and unbalanced load per phase.