Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). "2 September 2009." Includes bibliographical references (p. [139]-148) and index. Also available via the World Wide Web.

M.Ing. / With the advances in technology and the increase in industrial facilities, the harmonic content of an electrical network has always been a major concern among power system engineers. This is especially in an industrial environment, where the usage of power is very high as there are many large-scale types of equipment being used. Thus, it would be useful to know the sources, distortion level, impact on the power system and the equipment of harmonic currents on the harmonically rich electrical network. The presence of harmonics on electrical networks poses many problems to power system engineers and inconvenience or loss to the industries. Their effects on power system apparatus include resonance, reduced operating life of rotating machines and error in power calculations. For this study, the author would like to find out the implications of this issues, following these harmonic problems by analyzing, with some amount of simulations, practical measurements and assessments. In this way, a better understanding could be gained about these harmonic problems and harmonic contents. Steps could be taken to protect the power system equipment that could be affected by high harmonic currents and raise the quality of power supply.

The techniques of two-dimensional model seismology were employed to investigate the problem of Rayleigh waves incident upon the boundary between two solid elastic media. The object of the investigation was the determination of the reflection and transmission coefficients. As a preliminary, the special case of a quarter space was examined to test the hypothesis that the reflection coefficient could be successfully approximated by selecting the amplitude of the reflected Rayleigh wave so that the normal and tangential stresses imposed on the free surface are minimized in the least square sense. Analogously for the half space, it was proposed that the reflection and transmission coefficients should be such as to minimize the differences (or residuals) between the respective stresses and displacements on either side of the discontinuity. This is a reasonable assumption since the boundary conditions require continuity in this case. It was found that the agreement between the measured and calculated values of the coefficients was only qualitative and it had to be concluded that the proposed hypotheses were not sufficient to explain the reflection and transmission of Rayleigh waves. For a half space consisting of an aluminium alloy and plexiglass, the reflection and transmission coefficients were measured as a function of the angle with which the plane interface between the two media meets the free surface. The angle was varied in steps of 10° from 0° to 180° and the observed coefficients are presented with no attempt at a theoretical derivation. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis presents a comprehensive solution technique for power system harmonic analysis with unbalanced load flow conditions. It is based on multiphase modelling of the system in phase quantities. Two of the most important features of this technique are the multiphase approach to the harmonic load flow problem, and the capability to add component nonlinearities easily. The first feature allows the technique to be used for either single-phase or three-phase, and for either balanced or unbalanced harmonic analysis. The second feature allows the later addition of power electronic device models. The technique is simple in concept. The nonlinear elements are first modelled as harmonic Norton equivalent circuits based on the network load flow conditions. These linear circuits are then included in the network solution with multiphase load flow constraints and network unbalances. Once the new load flow solutions are obtained, improved Norton equivalent circuits can be calculated, which in turn are used for improved network solutions. The entire solution scheme is therefore iterative, and stops when certain convergence criteria are met. The unbalanced harmonics from nonlinear inductors, synchronous machines and static compensators with thyristor-controlled reactors are studied in this thesis. The convergence properties of the technique are investigated with test cases and theoretical analysis. In addition to the harmonic load flow analysis, this technique can also be used as an improved initialization procedure for the Electromagnetic Transient Program (EMTP). / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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M.Ing. / The increased used of non-linear loads within the power system during recent years have resulted in deviations from the perfect sinusoidal voltage and current waveform. This deviation from the perfect sinusoidal waveform can be expressed according to Fourier analysis by a set of co-sinusoidal waveforms having frequencies, which are a multiple of the fundamental frequency, referred to as harmonics. Non-linear loads are generally characterised by harmonic currents. It is therefore often preferred to express the harmonic emission limits in terms of harmonic currents rather than harmonic voltages. In order to translate the harmonic currents into harmonic voltages the harmonic impedance of the power system must be known. The power system's harmonic impedance can be assessed via computational, simulation and measurement techniques. The study will concentrate on the estimation of the harmonic impedance of a 33kV power system by implementing two online frequency domain measurement techniques. Both techniques are applied at the point of delivery of a dominant nonlinear load during normal and energisation load conditions with its power factor correction capacitor bank in and out off service. The estimated harmonic impedance is then compared with the calculated and simulated harmonic impedance.