No description available.

No description available.

Thesis (M.S.)--Ohio University, August, 1982. / Title from PDF t.p.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Includes bibliographical references (p. 65-69).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 131-132).

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed January 5, 2010). PDF text: vi, 157 p. : ill. ; 2 Mb. UMI publication number: AAT 3360085. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (M.S. in electrical engineering)--Washington State University, May 2007. / Includes bibliographical references (p. 70-73).

The research work conducted and presented forward in this document is the evaluation of real time values obtained using three recording devices at two independent locations and implementing them as recorder devices in Eskom’s power system. The research work conducted was presented at an IEEE International Conference (ICIT2013) and Appendix A shows the accepted paper presented. A derived model within a simulation software package known as DIgSILENT PowerFactory is created and Electromagnetic Transient (EMT) studies are performed and then compared to the real time values obtained using the OMICRON CMC 356’s. Transformers are normally energised via a circuit breaker which is controlled by an auxiliary closing contact. By applying system voltage at a random instant in time on the transformer windings may result in a large transient magnetizing inrush current which causes high orders of 2nd harmonic currents to flow under no load conditions. A philosophy known to mitigate these currents is to energise the transformer by controlling each individual phase 120 degrees apart with the first pole closing at the peak on the voltage waveform. Transients produced due to 500MVA transformers been introduced into the power system at a certain space in time can cause nuisance tripping’s at the particular location where the respective transformer is energised. OMICRON EnerLyzer is the software tool used for the Comtrade recordings at both locations. Four independent case studies are generated within EnerLyzer software and the relevant Comtrade files are extracted for the four independent case studies relative to Transformer1 and Transformer2 switching’s. TOP software, which is a mathematical tool used to analyse Comtrade files, is then used to analyse and investigate the four case studies. Results from DIgSILENT PowerFactory are then generated according to the derived model. The results extracted depict three scenarios, indicating a power system that is weak, strong and specifically a power system that correlates to the actual tripping of a Static VAr Compensator (SVC). The results are all formulated and then evaluated in order to produce a conclusion and bring forward recommendations to Eskom in order to effectively ensure the Dedisa/Grassridge power system is reliable once again.

The object of this research is to develop a satisfactory method for locating high-impedance faults in underground cables. Most methods of locating faults require that the fault-impedance be reduced to a low value before the measurement can be made. After a careful investigation of the available literature, it was decided that the most desirable method would be one utilizing the traveling-wave. Of the traveling-wave methods, the fault-generated surge method appeared to have the greatest possibilities; yet, according to the author's knowledge, this method has not been applied to power cables. In this method, the cable itself may be considered as the network that generates the required surges. The cable is initially charged to a voltage sufficiently high to establish an arc at the fault. The sudden collapse of the high voltage at the fault generates a surge which travels along the cable to the monitoring end, where it Initiates a timing device and is reflected back along the cable toward the fault. The arc which is still conducting reflects the surge back to the station. The time interval between the first and second arrival of the fault-surge at the station is recorded by the timing device and is proportional to the distance to the fault. In mathematically analyzing the surge phenomena in cables, the La Place operational method of analysis is used. The calculations for the transient produced by the discharge of a distortionless cable are worked out in full detail. The wave-form calculated is plotted and substantiated with experimental results. The transient produced is a rectangular wave that is exponentially attenuated and whose period is 4δ, where δ is the one-way transmission time of the cable in seconds. It is this wave-form generated by the cable itself that is used to locate the fault. Basically, the fault-locator developed consists of, a high-voltage low-current power pack, a triggering unit, a timing-pip generator, two uniform delay lines, and a double-beam oscilloscope. The block diagram of the fault-locator and the circuit diagrams of the triggering unit and timing-pip generator are given. The operation of the circuits and the procedure for measuring cable faults are fully explained. The fault-locator was tested on coaxial cable only, since no power cables were available. The results obtained were very satisfactory. The oscilloscope traces obtained were photographed and the experimental results discussed. It is concluded that the fault-locator can be used without modification for locating low and medium-impedance faults, as well as high-impedance faults in power cables. If the timing-pip interval is increased, the fault-locator can also be used for locating faults on overhead transmission lines. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate