Development of a model of the alpha/beta 765kV line for the evaluation of auto-reclosing.
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Date
2009
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Abstract
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.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2009.
Keywords
Electric current converters., Theses--Electrical engineering., Power electronics.