abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

The purpose of this work was to investigate teaching possibilities of the theme “Electric Current in Gases” in the course of Physics for secondary schools while using Information Technologies and their influence on teaching/learning process.

The intention of this dissertation is to determine, on the Eskom system, if the pre-insertion closing resistors installed on the Alpha-Beta 765 kV line breakers are preventing overvoltages from being caused during auto-reclosing. Other possible solutions of reclosing protection are investigated. It has been shown on two occasions, from actual field data that overvoltages have occurred on the lines after reclosing. High overvoltages on this network could be the cause of the many reactor failures that have occurred. A mathematical model of the Alpha-Beta 765kV system was produced on Matlab/Simulink to simulate the resonance of the line during opening and then the effect on the voltage when reclosing takes place. The effects of installing pre-insertion resistors to reduce overvoltages on reclosing were analysed, as well as looking at controlled reclosing at the optimal voltage across the line breakers. It was shown from the studies, that pre-insertion resistors do limit the overvoltages to within the surge capabilities of the line (10% overvoltage) and that the cause of the previous overvoltages were actually due to insertion resistor operations failure. It was also shown that the method of controlled closing at optimal voltage across the breakers is also a successful method of preventing overvoltages. This dissertation also evaluates a design specification for a switching relay for controlled re-closing of the line. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2009.

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Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 105-106). Also available on the World Wide Web.

Thesis (M.Eng.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 115-120.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: John Q. Xiao, Dept. of Physics and Astronomy. Includes bibliographical references.