System Thevenin impedance estimation through on-load tap changer action

Many of power system studies are based on a two-bus equivalent system where the supply system is represented by its Thevenin equivalent seen from the terminals of the bus of interest. In this paper a novel method is developed to estimate power system Thevenin impedance that uses the changes of the load bus voltage and current, caused by the on-load tap changer (OLTC) action. It is shown that the changes in the load voltage and current in the primary side of OLTC can be used to estimate the system Thevenin impedance. The proposed method is confirmed by simulation.