The effects of transformer connection type on voltage and current unbalance propagation

Unbalanced line currents cause unbalanced voltage drops on the three phases of the supply system. Consequently, the voltage system within the supply network will become unbalanced. Voltage unbalance has different detrimental effects in electrical power systems, such as the growth of losses in drive systems and adjustable speed drives, supplementary heating, line-current unbalance, derating, torque pulsation, mechanical stresses, etc. This paper makes an effort to have a comprehensive analysis of the effects of different connection types of three phase transformers on voltage unbalance propagation in distribution networks. The indices of voltage unbalance factor (VUF) and current unbalance factor (IUF) are used in this paper to evaluate the unbalance propagation. These indices are acquired utilizing symmetrical component theory on three phase voltages and currents earned through the system impedance matrix.