Theses and Dissertations (Power Engineering)

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    Partial discharge evaluation of a high voltage transformer
    (2015-02) Kyere, Isaac Kwabena; Walker, J. J.; Le Roux, B. J.
    This dissertation is devoted to the study of partial discharge evaluation of a high voltage transformer. The 400 V/300 000 V (300 kV) high voltage transformer in the high voltage laboratory was manufactured in 1967. Given the old age of the transformer and the crucial importance of insulation systems, it is vital to assess the condition of its insulation to ensure the effectiveness and the reliability of the transformer as well as the safety of the personnel using it. In order to achieve that, it is important to evaluate the partial discharge in the insulation system as this is the main cause of destruction of insulation. The phase-resolved partial discharge method was the main method used to perform the partial discharge measurements in this research. Partial discharge measurements were performed on a faulty 11 kV voltage transformer. Defects were also created in samples of solid insulation at predetermined locations with different shapes and sizes. The measurements taken on the 11 kV voltage transformer and samples of solid insulation formed a basis to prove the validity of the assessment methods on the 300 kV transformer. Using the method mentioned above, partial discharges were recorded with respect to the phase of the applied voltage with the aid of a commercial instrument which complies with IEC 60270, (ICM monitor - partial discharge detector from Power Diagnostix Systems GmbH). The observations from this study have furthered the understanding of partial discharge processes. The patterns recorded were analysed in order to conclude about the condition of the transformer. From the partial discharge pattern, the type and location of partial discharges were concluded. The patterns obtained from the transformer reveal that the device is healthy and can be operated up to 200 kV.
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    Design and development of a high efficiency modulated Class E amplifier
    (2006-01) Crafford, Crafford, Hendrik Lambert Helberg Hendrik Lambert Helberg; Pienaar, H. C. v Z.
    Amplitude modulation is not commonly associated with effective amplifying. This work focuses on implementing amplitude modulation into a high efficiency Class E amplifier. Different types of amplifiers are compared with each other, to show the advantages of using a Class E amplifier. The theory of the Class E amplifier is dealt with in detail. A harmonic filter is designed for the amplifier to make it radio spectrum friendly. The modulation process is implemented with the aid of a transformer into the Class E amplifier. The advantage of this is that the transformer serves both as a radio frequency choke for the Class E circuit as well as a modulator. The implementation of the amplitude modulation into the high efficient Class E circuit was successful. The final Class E circuit had superb efficiency, the harmonic filter showed good harmonic attenuation and the modulation process had low distortion. All this resulted in a fine low power AM transmitter.
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    Incandescent light power efficiency: an impact study on the power consumption of the Vaal University of Technology's light sources
    (2013-12) Adeniyi, A. O.; Sutherland, G.; Nicolae, D. V.; Joubert, T.
    In view of the energy consumption problems, an impact study, extensive laboratory tests and an investigation towards comparable energy saving light sources was carried out on the light sources identified in the survey conducted at the Vaal University of Technology (VUT), Vanderbijlpark campus. Three types of identified incandescent light sources were purchased and extensively tested in order to obtain viable statistical data on the life span, luminance delivered per unit, power consumption and economic effect, as well as identifying relevant energy efficient light sources for replacement purposes. A suitable computerised maintenance program has been developed to be introduced to the VUT that currently does not have a lighting system maintenance program. The case study was located within the empirical-analytical paradigm, using quantitative data. The identified aims and goals place the empirical part of the study in the category of implementation evaluation research that provides an overview of a maintenance plan.