Several monitoring, protection, and control applications designed for modern power grids are based on detailed grid models and thus require an accurate knowledge of line parameters. A synchronized monitoring infrastructure based on Phasor Measurement Units (PMUs) may be of great support to the task of line parameters estimation, but the accuracy of the estimated parameters may be largely affected by the uncertainty of all the elements of the PMU-based measurement chain. Thus, an accurate parameters estimation must appropriately consider the metrological behavior of all these elements, and in particular that of instrument transformers. To address this challenge, the paper proposes an enhanced multi-branch method for accurate estimation of the line parameters and of the systematic measurement errors introduced by the instrument transformers when measurements for multiple operating conditions are considered. Indeed, multiple operating conditions are dealt with properly, thanks to an in-depth analysis of the problem modeling within the framework of Tikhonov regularization. The validity of the proposed approach is confirmed by the results obtained on the IEEE 14 bus test system.
The availability of accurate data is fundamental for several monitoring and control applications of modern power grids. Nevertheless, the knowledge of critical data such as transmission line and transformer parameters is often affected by uncertainty. This can lead to important problems in the correct management of the power systems. In spite of a monitoring infrastructure that is being renewed thanks to new generation devices providing synchronized measurements, the actual values of line parameters and tap changer ratios are still affected by uncertainty sources that need to be properly considered. The behaviour of all the elements involved in the measurement chain must be duly modelled. This paper proposes an improved method to carry out the simultaneous estimation of line parameters, tap changer ratios, and systematic measurement errors for a three-phase power system. The proposed method is based on the suitable modelling of the measurement chain and on three-phase constraint equations (voltage drop and current balance) of all the components involved. Its effectiveness is confirmed by tests performed on a IEEE 14 bus test system reproduced as a threephase system under different operative conditions.
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