published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

An Integrated Power System (IPS) with a DC Zonal Electrical Distribution System (DC ZEDS) is a strong candidate for the next generation submarine and surface ship. To study the implementation of an IPS with DC ZEDS, members of the Energy Sources Analysis Consortium (ESAC) are currently constructing a reduced-scale laboratory. One fundamental component of DC ZEDS is the Ships Service Converter Module (SSCM), commonly known as a buck DC-DC converter. This thesis documents the design, simulation, construction and testing of a 500V/400V, 8kW resonant soft-switched DC-DC converter. In theory, resonant converters will operate more efficiently and generate less Electromagnetic Interference (EMI) when compared to a standard hard-switched converter. In this thesis, the resonant converter is tested and compared to a hard-switched DC-DC converter that was designed for ESAC's reduced-scaled IPS. The results verify that the resonant DC-DC converter realizes significant efficiency and EMI generation improvements over the hard-switched converter at the cost of a more complex control system and power section. / US Navy (USN) author

A dissertation submitted to the Faculty of Engineering. University of the Witwatersrand. Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. D.tT~.awart •• w1t~4i.tinotion on , Dec ••ber I,e7 Johannesburg. ItN7 / Accurate forecastinu of system Maximum Demand (MDl is vital ~o Esk011l. Under-estimating the MD could re-ul: in a generation capacity shortage. with devastating consequences for the economy. Similarly. a high MD forecast would result in overcapacity. with expensive generating plant standing idle The traditional method of MD forecasting in Eskorn has become unreliable due to a changing relationship between forecast energy sales and expected maximum demand. The reasons for the changing system demand profile were isolated and analysed. Alternative MD forecasting techniques are evaluated and end-use hourly aggregation modets were ;d'~ntifieJ as a method suitable for Eskorn, An experimental demand profile forecasting moue! was developed, using data from a previous project. The model was tested and proved able to cope with the structural changes in the system demand profile. This resulted in the adoption of this technique by Eskorn and approval for the devclopn-ent of a f\.JJ1 scale de manu profile forecasting model.

Abstract With an ever increasing emphasis on reliability of supply, improvement in the lightning performance of distribution lines is required. The arc quenching properties of wooden distribution line poles during lightning strikes are an important factor in the reduction of switchgear operation, hence outages. Measurements were conducted on a 22 kV distribution line and it was suspected, in some cases, that direct lightning strikes to the line did not cause switchgear operation. Distribution lines predominantly use wooden poles with a specific configuration which incorporates a 'wooden' spark gap. This paper provides background to the basic configuration of a typical distribution line and the processes which govern the electric arc. A simulation using a dynamic arc model shows that field measured lightning overvoltages on a distribution line are reproducible through system modelling. The simplistic dynamic arc model developed is sufficiently accurate to describe a set of arcs in a larger system such as a distribution line.

Lu, Lian. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 91-95). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.

My dissertation tells the history of the Electric Power Research Institute (EPRI), the U.S. electric utility industry’s collective technology organization, founded at the onset of the successive “Energy Crises” of the 1970s. The narrative tells a history of EPRI in three registers: the organization, the people, and the ideas. It tracks the internal politics of the industry’s research and development arm through each of its five sectors—nuclear generation, fossil fuel generation, environment and safety, end use, and transmission and distribution. Each sector was buffeted by EPRI’s management history, what one EPRI career project manager dubbed, “Peace, a Civil War, and the Great Depression.” Embedded in each of these sector histories is story of the incremental shift from one regulatory regime, a “natural monopoly,” to an as-of-yet unrealized regime, the “self-regulated network.” When deregulation was imminent in the mid-1990s, utility executives decided that collaboration and competition were at odds. EPRI funding plummeted by half. Instead of making it to the aspired destination at the “self-regulated electricity network,” American power got stuck in an impasse I call, with irony, the “networked grid.” The “networked grid” is a rigid grid with information and communication technology laid on top so as to achieve the illusion of economic efficiency at the cost of reliability, security, sustainability, and physical efficiency.

Dissertation submitted for Masters of Science degree in Mathematical Statistics in the Faculty of Science, School of Statistics and Actuarial Science, University of the Witwatersrand Johannesburg May 2016 / Electricity demand in South Africa exhibit some randomness and has some important implications on scheduling of generating capacity and maintenance plans. This work focuses on the development of a short term probabilistic forecasting model for the 19:00 hours daily demand. The model incorporates deterministic influences such as; temperature effects, maximum electricity demand, dummy variables which include the holiday effects, weekly and monthly seasonal effects. A benchmark model is developed and an out-of-sample comparison between the two models is undertaken. The study further assesses the residual demand analysis for risk uncertainty. This information is important to system operators and utility companies to determine the number of critical peak days as well as scheduling load flow analysis and dispatching of electricity in South Africa. Keywords: Semi-parametric additive model, generalized Pareto distribution, extreme value mixture modelling, non stationary time series, electricity demand

Thesis (Ph. D. in electrical engineering)--Washington State University, December 2007. / Includes bibliographical references (p. 135-146).

Today's power systems are undergoing dynamic changes in their operation. The high cost of capital improvements that include new generation and transmission projects has prompted power system planners to look for other alternatives in dealing with increased loads and overall system growth. A dynamic braking resistor is a device that allows for an increased rating of a transmission system's transient stability limit. This allows increased power flows over existing transmission lines without the need to build additional transmission facilities. This thesis investigates the application of dynamically controlled resistive braking in the Pacific Northwest power system. Specifically, possible control alternatives, to replace the present dynamic brake control system at Chief Joseph station, are examined. This examination includes determination of appropriate locations for control system input, development of control algorithms, development of computer and laboratory power system models, and testing and recommendations based upon the developed control algorithms. / Graduation date: 1995