3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Investigation into the issues associated with closing an automated Normally Open (N/O) point on three Medium Voltage (MV) Networks where Fault Location, Isolation and Service Restoration (FLISR) is planned(2019) Mthethwa, FundiswaThe design of Medium Voltage (MV) Overhead Lines (OHLs) in the electricity distribution industry is often radial in nature which makes back-feeding difficult and these networks are often long which increases their exposure to faults. This has resulted in poor network reliability. Customers are mainly affected by faults on the MV network, to which particular attention has to be paid. Permanent faults have negative impact on customers since they experience outages or interruptions. The impact on customers increases when these outages are long. The network reliability is reducing and the cost to customers is increasing. Customers are demanding higher levels of quality of supply from the distribution network. As the global energy study is working on achieving the seventh Sustainable Development Goal (SDG 7), it is important to have a reliable power supply to improve socioeconomic development to customers and this will be a stepping stone in achieving other SDGs. Digitalization is one of the factors affecting electricity networks towards a clean energy future and automatic service restoration is one of the most important strategies for Distribution Automation (DA). Therefore it is necessary to implement self-healing Smart Grid technologies. One such solution is Fault Location, Isolation and Service Restoration (FLISR). The main drive towards FLISR is to improve Eskom’s network performance, improve electricity sales, flexibility and accessibility and reduce impact on the economy of outages as well as to support trends towards a more sustainable energy supply. This research investigates various ways to implement FLISR and it focuses on case studies on real distribution networks and looks at the issues associated with closing a remotely controlled or automatically operated Normally Open (N/O) point for back-feeding. The complete algorithm and procedure of autorestoration are discussed. The results on case studies discussed in this dissertation show that a remotely controlled N/O point can be installed without constraining the network to reduce restoration time following a fault. This is assured by not violating network’s electrical requirements such as voltage levels and feeder thermal loadingItem Emerging behaviours in artificial societies: simulating social-economic phenomena(2018) Ingram, Branden CorwinThe behaviour of a society and its individuals is inherently complex and, therefore it becomes difficult when trying to model how changes in a society will affect that population. This dissertation presents an implementation of a computer simulation technique known as an Artificial Society, which is used to model social-economic phenomena using a multi-agent system. An Artificial Society is a system of simulated agents in a simulated world governed by a set of rules which handle the nature of the interactions between entities of the system. The purpose of this model is to analyse the emergence of global behaviours that form from the evolution of the society as a result of interactions governed by simple rules. We firstly expand on a number of aspects of the work done by Epstein and Axtell [1996] such as trade and cultural transmission. We analyse the similarities of our model with that of pre-existing models such as the Predator-Prey model. We demonstrate the spread of culture through a society and investigate the influence an individual can have on a population in different environments. We also investigate and analyse the benefits and shortfalls that different kinds of trade, taxation and investment can have on a society in a 3 resource environment. Through all of these experiments, we were able to demonstrate the emergence of complex behaviours which formed as a result of the interactions of individuals. This approach of modelling whereby we generate simple rules and observe the emergence of global behaviour is gives us the ability to tackle modelling complex behaviours where using a closed form solution would be impractical. It is hoped that this study will inform readers on the potentials and benefits of Artificial Societies.Item The optimally diversified equity portfolio in South Africa: an artificial intelligence approach(2017) Block, Aaron EliyahuDiversification has remained a central tenet in investment theory over multiple decades due to its demonstrated value as a risk mitigation technique. Increasing the number assets in a portfolio, where the magnitude of correlation is relatively slim, increases the amount of diversification while also encountering increased costs in the form of transaction costs, taxes and the like. Thus, it is imperative to solve for the optimal point of diversification to ensure an investor does not encounter unnecessary costs. This study aims to solve for the point of optimal diversification in an equity portfolio, focusing on the South African environment. This is achieved by employing a framework using both the traditional simulation method as well as more advanced mathematical techniques, namely: genetic programming and particle swarm optimisation. Marked improvements are realised in this study with regards to the methodology and results through the application of advanced mathematical approaches in addition to removing the restriction of equal weightings being applied to each share in the portfolio. The results revealed that an optimal portfolio can be constructed using up to only 15 shares. Secondly, the genetic programming approach demonstrated increased strength compared to the traditional simulation and particle swarm optimisation approaches, obtaining a greater level of diversification with fewer shares. Finally, although the aim of the study is focused on modelling the relationship between the number of shares in a portfolio and the achievable diversification benefits, it is also established that the portfolios indicated as being optimally diversified achieved market beating returns.