Novel approach in state estimation for unbalanced transmission systems

A state estimation approach for unbalanced transmission systems is presented. The phasor measurement units (PMU) are used to measure negative and zero sequence voltages and currents relevant to asymmetrical lines so that accurate line models can be incorporated into a state estimation algorithm. The method is formulated as an extension of existing state estimation algorithms. It means that the existing state estimation programs can be used with minor changes and extra coding for negative and zero sequences should be added. The advantages of the technique are demonstrated by using test power system with untransposed lines.