Online estimation of power transmission line parameters, temperature and sag

This paper puts forward a framework for estimating transmission line parameters (including series resistance, reactance and shunt susceptance), line temperature and sag utilizing synchronous voltage and current phasors measured by the phasor measurement unit (PMU) in real time. Transmission line parameters are essential inputs to various power system analyses and applications such as power flow analyses and protective relaying applications. The estimated line temperature and sag can be utilized in dynamic thermal rating applications for increased power transfer. Different types of transmission line topology are classified and modeled to facilitate the development of corresponding algorithms. The proposed least square algorithms harness the nonlinear optimal estimation theory, and are capable of detecting and identifying bad measurement data, minimizing the impact of measurement errors and thus significantly improving the estimation accuracy. In addition, this paper studies an optimal approach for placing PMUs in order to determine the line parameters, temperature and sag. Numerical examples and preliminary results are presented.

I. Introduction

The power system analysis of transmission lines requires transmission line parameters, including series resistance, series reactance and shunt susceptance as important input quantities to various applications, such as protective relaying algorithms and power flow analyses [1] [2]. It is highly desirable to develop effective online programs for estimating these line parameters. The precision of line parameters obtained from those programs is also essential in ensuring the reliability and accuracy of the analyses [3] [4].