A study of winding failure modes in laboratory scale transformers

Li Zhu

    Research output: ThesisMaster's Thesis

    896 Downloads (Pure)

    Abstract

    The population of power transformers in industry is aging. Failures of power transformers induce catastrophic consequences like fire, electric system outages or even loss of life. Therefore, in the past few years, researchers and industry people have been focussed on developing methods to better understand the risk/ life assessment of power transformers. This project develops and safely conducts laboratory scale test procedures to investigate the behaviours and effects of specific winding failure modes in laboratory scale transformers. The aims of this project are to develop and test process to (1) Initiate specific winding failures in a safe and repeatable manner in the laboratory, (2) Observe the behaviour of the transformer failures, (3) Explore the influence of environmental factors that may accelerate the failure progression, (4) Observe the behaviour of the tested transformer under different conditions. The results show the effect of time on the winding temperatures change when the transformer is overloaded. A thermal model of the heat transfer of transformer windings is developed. By monitoring the temperature of the winding surface and the current through the windings, the hot spot temperature can be calculated. Before the hot spot temperature reaches too high and generate an overheating or short circuit failure, actions can be taken to prevent losses of transformers. Transformer vibration is measured and the results show that at low frequencies, the vibration result of a core-loosened transformer is not significantly different from that of a healthy one. At high frequencies, the vibration result of the transformer with core loosened has more harmonics than that of a healthy one. This appearance of additional harmonics is a potential criterion to identify the core-looseness failure of a transformer.
    Original languageEnglish
    QualificationMasters
    Publication statusUnpublished - 2011

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