Abstract
Data concerning actual temperatures of line conductors constitutes essential information for the power system operator. The temperature of the power lines can be used to improve the accuracy of the power system model, thereby increasing the accuracy of the state estimation. This article presents a two-step algorithm for the power system state and line temperature estimation. In its second stage, the proposed method searches for a line temperatures vector, which corrects the uncertain power system base model and allows for further minimization of an objective function. As a result, a more accurate estimation is obtained along with a more precise model of the estimated system. The derived model can then be used for more accurate optimization. The presented method enhances standard procedures of power system state estimation, and its advantage is that it does not require direct measurements performed by phasor measurement units or measurements of line conductor temperatures and weather conditions realized by dynamic line rating systems. The results of simulations made on various test models have been examined, confirming the convergence of the procedure to the point at which the average temperature of the line wires together with the voltage values and phase angles are achieved. The algorithm’s performance and improvement method have also been presented. An advantage of the investigated approach is the possibility to calculate the temperature of line wires with the use of primary measurements in the power system. The presented and examined method, however, is sensitive to the measuring device errors. Additionally, an analysis of the method’s errors and ways of reducing them has been performed.
Highlights
Modern power systems should have the possibility of flexible power transmission, which is directly related to the more extensive use of Overhead Transmission Line (OTL) capabilities, especially when it comes to high penetration of renewable energy sources [1,2]
State estimation of an electric power system is performed based on measurement data encumbered with errors
A power system model that is used for the estimation purposes deviates from real parameters, because of the applied simplifications and modeling errors
Summary
Modern power systems should have the possibility of flexible power transmission, which is directly related to the more extensive use of Overhead Transmission Line (OTL) capabilities, especially when it comes to high penetration of renewable energy sources [1,2]. A two-step power system state and line temperature estimation is proposed that uses only classical measurements such as active and reactive power, bus voltage and current, without any additional measurements such as ambient parameters from weather stations, conductor temperatures from DLR, voltage and current magnitudes with its angles from PMUs or Wide Area. The accuracy of the temperature estimation method mainly depends on measuring apparatus classes This approach allows us to determine the OTLs without additional measured values, but it increases the demand for computing power. The inaccuracy of the power system model results mainly from the actual temperatures of the operating conductors of the power line, which in the case of accurate measurements causes errors in the estimation of the state.
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