Determining transmission line parameters from time-stamped data

Abstract

The main aim of this project was to find a practical and accurate method to determine the parameters of a transmission line by using current and voltage measurements. The term line parameters refer to the inherent series resistance and inductance that is found on transmission lines. The line parameters were determined by using the voltage and current measurements from either side of the transmission line. An accurate reference signal is needed to precisely compare the measured signals. The timing signals from GPS units were used to reference the measurements. In a field implementation data transfer of the measured signals would be a necessity which can be accomplished by GPRS modems. Three methods are proposed for determining line parameters. These methods were thoroughly tested in the following ways: 1. A model was built in SIMULINK with known elements and values. The three methods were then applied to the model and simulations were run. The results from the simulations are compared to the known values. 2. A system was built in the laboratory with known parameters. The results gathered from testing the system on all three methods are compared to known values. 3. Finally, the methods were applied to field data from recorders of a utility. This was done to see how well the methods would perform on a real system. Accuracy was determined from what the utility accepts as the correct values. Another focus of the project was to determine the surge impedance loading (SIL) curve from measured data. This curve can be used to determine the loadability limit of the transmission line as well as to visually show at what point the line is operating at any given time. The curve is also useful as it provides insight into the additional reactive power needed for a certain active power transfer. The concept of drawing a SIL curve from actual measurements was first tested by means of simulation. The drawing of the proposed curve is also tested on actual measurements from a transmission line. This investigation posed many challenges. These challenges are discussed in detail in the dissertation. Some of these challenges have easily implementable solutions while others still leave room for further research. The results and findings are published in this document.