A FEASIBILITY STUDY FOR PROTECTING TRANSMISSION LINES USING TRAVELING WAVES
Date
2003
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ORCID
Type
Degree Level
Masters
Abstract
Faults occur in power systems because of the failure of insulation and structures. The faults almost always result in the flow of large quantities of currents. Protective relays are used, therefore, for detecting the faults and isolating the faulted section of the system before the damage spreads. Traditionally, electromechanical and static technologies have been used for designing and manufacturing relays. More recently, advancements in the VLSI technology have resulted in the development of microprocessor-based numerical relays. Several algorithms have been proposed in the past, which are suitable for using in numerical relays for detecting the occurrence of faults. These algorithms convert the samples taken from the waveforms to phasors of the fundamental and harmonic frequencies. The conversion techniques usually take time that is at least one-cycle of the fundamental frequency. This time is 16 ms for a 60 Hz system and 20 ms for a 50 Hz system.
This thesis describes two techniques for designing high-speed numerical relays. The first technique uses sampled voltages and currents from the local terminal of the line. The second technique uses samples of voltages and currents from the local terminal and processed information from the remote terminal of the line. Both techniques are based on the arrival of traveling waves starting by the onset of faults. The first differences are used to detect the instants of the arrival of the voltage and current traveling waves.
The performance of the proposed techniques was investigated by computer-based simulations. Different types of faults on different locations in a sample power system were simulated using the electromagnetic transient program, EMTDC. The impacts of
hardware constraints were also evaluated. Some of the cases investigated during this project are reported. The results indicate that the proposed techniques are suitable for protecting a transmission line. Their operating times are less than 4 ms compared to 10 ms or more for the presently available relays.
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Degree
Master of Science (M.Sc.)
Department
Electrical Engineering