Thesis (M.S.)--University of Wisconsin--Madison, 1957. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, June 1997. / Thesis advisor, Robert W. Ashton. "June 1997." Includes bibliographical references (p. 149). Also available online.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009. / Full text also available online. Scroll down for electronic link.

[No abstract available] / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The object of this thesis is to find a method for locating transient as well as permanent faults on transmission lines. Transient faults are those lasting for a fraction of a second or so which do not cause serious enough damage to necessitate immediate repairs before the line may be reenergized. However, transient faults such as insulator flashovers may cause enough damage to be a potential permanent outage. It is thus desirable to be able to locate the position of the fault, and to inspect the line and insulators so that they may be repaired if necessary when the line can be conveniently removed from service. The method that seemed most desirable was based on the echo-ranging principle such as is used in radar. This method has the advantages of accuracy and ease of interpretation. A damped sine wave pulse is generated at short intervals and fed onto the transmission line by means of a coupling capacitor. This pulse travels along the line and is partially reflected from any discontinuity such as a flashover to ground. The transmitted pulse, and pulses reflected from the end of the line and the fault are shown on a viewing tube; the distance to the fault being found by proportion. The line is pulsed only on the occurrence of a fault; thus any interference with radio is eliminated. The pulse generator is tripped by zero-sequence current or from the surge created by the fault itself. The pulses were to be recorded on a skiatron or memory tube which holds the trace on the tube until it is erased at will by the operator. This eliminates the necessity of photographic equipment and the disadvantages of delay and inconvenience of developing the film. The work accomplished on the project included the theory of wave propagation along transmission lines and the reflection to be expected for arcing ground faults. A pulse generator was built to produce either a damped sine wave or a sharp-fronted wave with exponential decay. Experiments were -carried out on coaxial cable with carbon and oil arcs as the fault, but no experiments were carried out on actual transmission lines as no line was available. The results of these experiments and the theory indicate that the method should be satisfactory on transmission lines. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

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.

The electric power distribution system usually operates a radial configuration, with tie switches between circuits to provide alternate feeds. The losses would be minimized if all switches were closed, but this is not done because it complicates the system's protection against overcurrents. Whenever a component fails, some of the switches must be operated to restore power to as many customers as possible. As loads vary with time, switch operations may reduce losses in the system. Both of these are applications for reconfiguration. The problem is combinatorial, which precludes algorithms that guarantee a global optimum. Most existing reconfiguration algorithms fall into two categories. In the first, branch exchange, the system operates in a feasible radial configuration and the algorithm opens and closes candidate switches in pairs. In the second, loop cutting, the system is completely meshed and the algorithm opens candidate switches to reach a feasible radial configuration. Reconfiguration algorithms based on linearized transshipment, neural networks, heuristics, genetic algorithms, and simulated annealing have also been reported, but not widely used. These existing reconfiguration algorithms work with a simplified model of the power system, and they handle voltage and current constraints approximately, if at all. The algorithm described here is a constructive method, using a full nonlinear power system model that accurately handles constraints. The system starts with all switches open and all failed components isolated. An optional network power flow provides a lower bound on the losses. Then the algorithm closes one switch at a time to minimize the increase in a merit figure, which is the real loss divided by the apparent load served. The merit figure increases with each switch closing. This principle, called discrete ascent optimal programming (DAOP), has been applied to other power system problems, including economic dispatch and phase balancing. For reconfiguration, the DAOP method's greedy nature is mitigated with a backtracking algorithm. Approximate screening formulas have also been developed for efficient use with partial load flow solutions. This method's main advantage is the accurate treatment of voltage and current constraints, including the effect of control action. One example taken from the literature shows how the DAOP-based algorithm can reach an optimal solution, while adjusting line voltage regulators to satisfy the voltage constraints. / Ph. D.

Analysis was performed to quantify and compare the reliability of several different notional shipboard DC distribution system topologies in serving their equipment loads. Further, the relationship between the relative placement of loads and generators within a distribution system and the system’s reliability was investigated, resulting in an algorithmically-derived optimal placement configuration in the system topology found to be the most reliable in the initial analysis. Using Markov models and fault-tree analysis, system reliability indices were derived from distribution system component reliability indices, and these values were compared between competing topologies and equipment configurations. A distribution system based on the breaker-and-a-half topology often used in terrestrial utility substations was found to be superior in terms of reliability to the currently-standard ring bus topology. Expected rates of service interruptions to equipment systems served by the breaker-and-a-half system were reduced overall, in some cases dropping dramatically to less than one expected interruption per 10,000 years. This improvement, however, came at the expense of requiring more circuit breakers in the distribution system’s construction. Within this breaker-and-a-half distribution system, an optimal placement of loads and generators was algorithmically derived, which further improved the reliability of the system. This improvement over the base case was marginal, but the optimized placement configuration was able to reduce the expected interruption rate of the ship’s radar system by over 40%. / text

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