A thesis submitted to the Faculty of Engineering at the University of the Witwatersrand,
Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. / Particularly at the higher system voltages, certain faults have been attributed to VFTs. This work
presents a full frequency domain mathematical model of the effects likely to be introduced by
the application of a thin ferromagnetic coating to the surfaces of the busbars as a means of
attenuating these transients. Experimental verification shows the model to perform accurately
as an analysis tool for a continuous coated co-axial system. While comparison between the
model developed here (based on a planar conductor) and the very accurate Bessel function
solution is presented, it must be remembered that it is not feasible to include the effects of
coatings in the latter solution. Hence it is used merely as a bench-mark for improvements to the
general model. Consideration is also given to the transient skin effect, and this is shown to result
in an increased attenuation of VFTs. detectable during high voltage experimentation. The frequency
domain model is extended to that of a full travelling wave model for VFTs in GIS. The
Fourier technique is used to move between the frequency and time domains. Laboratory results
obtained at high voltage.show that this technique will introduce both risetime increase and peak
magnitude attenuation of VFTs. As the most frequent faults directly attributable to disconnector
operation are known to be faults to earth at the switch, it is noted that the technique proposed
in this work is uniquely suited for use in a design strategy that requires totally robust disconnectors
at the expense of more severe VFTs in the GIS. The model is used to determine a range
of physical characteristics of materials suitable for use in this application. While the
characteristics of the most suitable materials have therefore been established, it is concluded
that extensive metallurgical experimentation remains before this technique may be economically
applied. / Andrew Chakane 2018
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/25459 |
| Date | January 1990 |
| Creators | Jandrell, Ian Robert. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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