ETD Collection

Permanent URI for this collectionhttps://wiredspace.wits.ac.za/handle/10539/104


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2015 - 20182

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Subject: search.filters.subject.Lightning protection

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    A Bayesian framework for forensic investigations involving lighting location system data
    (2018) Hunt, Hugh Gordon Patrick
    The work presented in this thesis extends and contributes to research into the forensic use of Lightning Location Systems and the uncertainty present due to location errors. While previous work in this area has produced some approaches that can be used in forensic investigations, there has not been a consistent, standardised approach to presenting Lightning Location System stroke reports as evidence in a legal environment. In the research presented, a Bayesian framework for representing Lightning Location System data as likelihood ratios and posterior probabilities is developed. The statistical models necessary for use of the framework are discussed and verified through groundtruth events and bivariate statistical analysis. Photographs of multiple lightning events to the Brixton tower in South Africa and current measurements at the Gaisberg tower in Austria are used as ground-truth data and bivariate statistical techniques are used to fit and evaluate different statistical models. It is shown that the bivariate Students’ t-distribution is the best fit for Lightning Location System location errors, rather that the commonly assumed bivariate Gaussian distribution and that a bivariate Gaussian Mixture Model can be used to describe the prior probability of lightning occurrence in a region. It is demonstrated how the Bayesian framework can be used to present Lightning Location System data as evidence in a court of law. This represents a unique and valuable contribution to those working in the field of lightning location and, in particular, in forensic situations.
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    An approximation to the Heidler Function with an analytical integral for engineering applications using lightning currents
    (2015) Terespolsky, Brett Ryan
    The work presented contributes to research in lightning protection simulations and focuses on approximating the Heidler function with an analytical integral and hence a frequency domain representation. The integral of lightning current models is required in the analysis of lightning events including the induced effects and frequency analyses of lightning strikes. Previous work in this area has produced very specific forms of the Heidler function that are used to represent lightning current waveshapes. This work however focuses on a generic solution with parameters that can be modified to produce any lightning current waveshape that is required. In the research presented, such an approximation is obtained. This function has an analytical solution to the integral and hence can be completely represented in the frequency domain. This allows for a true representation of Maxwell’s equations for Electromagnetic (EM) fields and for an analytical frequency domain analysis. It has parameters that can be changed to obtain different waveshapes (10/350, 0.25/100, etc.). The characteristics of the approximation are compared with those of the Heidler function to ascertain whether or not the function is applicable for use with the lightning protection standard (IEC 62305-1). It is shown that the approximation does represent the same characteristics as those of the Heidler function and hence can be used in IEC 62305-1 standardised applications. This represents a valuable contribution to engineers working in the field of lightning protection, specifically simulation models.