A thesis submitted to the Faculty of Engineering, University of the Witwatersrand,
in fulfilment of the requirements for the degree of Doctor of Philosophy in
Electrical Engineering. / Lightning causes electrical shocks to people, the premature ignition of
explosives, and the ignition of methane underground in coal mines. This
study examines this problem using a theoretical study and the results of an
extensive measurement programme that was conducted in several coal mines.
The work that has been done, particularly in South Africa, is also reviewed.
Two mechanisms are responsible for the penetration of lightning surge
currents into the underground workings. A direct strike to the service
structures leading into a shaft is one of the two mechanisms, and the second
is that resulting from lightning strikes to the strata above the underground
workings.
The frequency and amplitude with which such surges can be expected is
quantified using the theoretical study. This model correlates well with the
observed frequencies of the empirical studies.
The sensitivity of methane to lightning-type sparks is investigated. Currents
as low as 10 rnA have been proved to be capable of igniting methane. The
sensitivity of conventional detonators is also investigated. The thesis
proposes a generalised test which can be applied to both the low-impedance
protection method and a high-impedance protection method. The test
methodologies have been generalised to make provision for any new
innovative detonators that may be used by the industry.
A risk evaluation of mines is developed which allows a mine to be
categorised according to the likelihood of lightning causing an accident in a
mine.
The South African Recommended Practice for avoiding such accidents is also
reviewed. / Andrew Chakane 2018
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/25064 |
| Date | January 1995 |
| Creators | Geldenhuys, Hendrik Jacobus. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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