Measurement-Based Improvement of the Accuracy of Transmission Line Parameters

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Dr. Raisz Dávid Márk
Department of Electric Power Engineering

An article was published in Elektrotechnika journal in 2009 witch discussed that MAVIR discovered serious anomalies about transmission line parameters (positive and zero sequence series resistance and inductance and shunt capacitance). For this reason these parameters needed to be determined more precisely. There are some computer programs available for this task which define these parameters by calculations using the geometrical and electrical characteristics of the transmission line as initial data.

The question came up, how it is possible to determine the power line parameters using measurements and what is the maximum accuracy that can be achieved with such a method? An instrument was developed at the Department of Electric Power Engineering for this purpose, which can record GPS synchronized current and voltage values at both terminals of the transmission line. My consultant worked out the basics of a procedure which can determine the transmission line parameters using these recorded values. My first task was to check the accuracy of this procedure, in order to decide whether it is worth measuring these parameters.

The transmission lines are located in a continuously changing environment. These environmental factors can affect the power line parameters e.g. the sag changes with the temperature. So the parameters cannot be treated as constant during the whole period of the measurement.

I ran computer simulations to determine how the sag affects the power line parameters.

I intend to introduce the method for calculating transmission line parameters, revealing the deficiencies of the processes described in the literature.

In the second part of this paper I present the results of the computer simulations.

Using real measurement data I had an opportunity to test our method and evaluate the recorded data. In the third part I present the results of this process.

It is a very important task to choose the data for the parameter estimation from the huge database of recorded current and voltage values. In the last part I outline the procedure I worked out and used.


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