Three-phase state estimation in transmission networks with unbalanced loading utilising SCADA measurements

Abstract

State estimation stands as one of the most crucial applications in energy management systems of control centres, ensuring the secure operation of the power system. The real-time availability of accurate system variables, including voltages, currents, and power flows, presents an excellent opportunity to consider the actual network characteristics, including imbalances. This paper presents a linear and non-iterative method to solve the three-phase state estimation problem in transmission systems with unbalanced loading. The method utilises supervisory control and data acquisition measurements obtained from remote terminal units. The formulation is based on complex variables derived from traditional supervisory control and data acquisition measurements, with assumptions made regarding the availability of certain three-phase bus voltages, as well as a number of three-phase currents and active and reactive power flows. The proposed algorithm employs the classical weighted least squares technique for solving the three-phase state estimation problem. Due to its straightforward and linear nature, the method ensures no convergence issues. To validate its effectiveness, the proposed method is validated on a three-bus network and the IEEE 39-bus network simulated using the three-phase model within the DIgSILENT Power Factory environment.