INVESTIGATION OF IMPACTS OF DIFFERENT 3-PHASE TRANSFORMER CONNECTIONSAND LOAD MODELS ON UNBALANCE IN POWER-SYSTEMS BY OPTIMIZATION

This paper investigates the impacts of different three-phase transform er connections and load models on unbalance in power systems. New thre e-phase transformer models are presented. These models are derived fro m a new primitive impedance matrix incorporated with positive, negativ e and zero sequence elements. The constant power and constant impedanc e load models are discussed. The three-phase models are implemented in a general-purpose optimization software package. Two power systems ar e used to illustrate the test results. The test results provide assist ance to engineers in understanding the effect of different connections on the transformers. This paper also emphasizes that a proper load mo del should be used; otherwise, an incorrect solution will be obtained.