A PMU-based Technique for the Simultaneous Estimation of Systematic Measurement Errors, Line Parameters and Tap Changer Ratio

Accurate monitoring tools are fundamental for the proper operation of the transmission grids. In this context, an essential requirement for the transmission system operator is the availability of accurate knowledge on transmission line and transformer characteristics. Despite the high accuracy of the increasingly used Phasor Measurements Units (PMUs), there are still significant issues associated with the knowledge of the actual line parameters and on the actual tap changer ratio. In this regard, the paper proposes a method to estimate simultaneously the line parameters, the tap changer ratio, and the systematic measurement errors associated with the instrument transformers. With an appropriate model of the measurement chain, which includes the uncertainties associated with instrument transformers and PMUs, a linear formulation of the line and transformer constraint equations can be applied and accurate results can be obtained. The validity of the proposed method is confirmed by different types of tests performed on the IEEE 14-bus test system.