Uncertainty propagation in PMU‐based transmission line monitoring

Abstract

This study analyses the uncertainties of synchronised phasor measurement-based transmission line monitoring applications. Uncertainty propagation is analysed in order to assess confidence in the accuracy of such monitoring applications and explain how systematic measurement errors affect the monitored quantities. Estimation of transmission losses and transmission line parameters is analysed as examples. The uncertainty analysis considers the entire measurement chain, i.e. it includes the measurement errors of instrument transformers and phasor measurement units (PMUs) and the propagation of resulting uncertainties into quantities of interest. The study adopts the principles of evaluating the uncertainties and their propagation in complex (i.e. two-dimensional) quantities, as this would be the most appropriate approach for phasors that can have different uncertainties in magnitude and angle. The study demonstrates how uncertainties of measured voltages and currents are propagated into the estimated quantities and what accuracy can be expected from such monitoring applications in a common transmission system setting. The study also helps to understand better what causes most of the uncertainty (and inaccuracy) in particular quantities of interest. The analysis is carried out on real PMU measurements of an operating transmission line.