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The parameters of the transmission lines are used in several monitoring and control tools of the power system control center. An accurate knowledge of the power system model (including transmission lines impedances) impacts positively the situational awareness of the power system operators. It also improves the protection and corrective measures that may be applied in case of a disturbance. Nevertheless, line parameters that are stored in the control center database are typically subjected to errors, and therefore it is necessary to regularly refine them. The presence of a phasor measurement unit (PMU) at both ends of the transmission line allows the calculation of the transmission line parameters using synchronized current and voltage phasor measurements. Although the use of PMU measurements is a straightforward way to calculate the transmission line parameters, the uncertainty of the synchronized phasor measurements should be incorporated to the calculated transmission line parameter values. In this paper, an analytical expression for the bounds of the calculated transmission line parameters from PMU measurements is derived, considering both instrument transformers and PMU errors. The calculated bounds of uncertainty are evaluated through Monte Carlo simulations, while the importance of knowing the bounds of the calculated line parameters is underlined through the derivation of power–voltage curves considering the lower and upper bounds of the parameters. The simulation results are obtained using the IEEE 14-bus system. [ABSTRACT FROM AUTHOR]

The state estimator constitutes the cornerstone of the supervisory control and data acquisition system since it provides the power system operating situation in consecutive time intervals. Furthermore, the output of the state estimator is used by other tools responsible for the monitoring and control of the power system. Therefore, there is a need for the power system state estimator to be as accurate and reliable as possible. The main source of uncertainty that may deteriorate the accuracy of a weighted least squares (WLS) state estimator, provided that the network parameters are perfectly known, is the uncertainty that is encompassed in the measurements. It is well known that the measurement chain is not ideal and this information is passed to the state estimator through the measurement weights. In this paper, the effect of the measurement weights, which are calculated by considering both the standard uncertainties associated with the measurement devices and the instrument transformers, on the WLS state estimator is examined. [ABSTRACT FROM PUBLISHER]

This paper computes the uncertainties associated with the power system state variables obtained with the help of phasor measurement units (PMUs). An integer-quadratic- programming-based method is used to determine the minimum number and the optimal locations of the PMUs to ensure complete topological observability of the system. Three approaches are used to estimate the uncertainties in the state variables: the use of the classical uncertainty propagation theory, the Monte Carlo method, and the random fuzzy variables (RFVs). The methods are applied on a test system, and the results are presented. The choice of method depends on the application; suggestions are offered based on the conclusions of the work in this paper. [ABSTRACT FROM AUTHOR]