Smart Grid Distribution Transformers: Empirical Design and Dynamic Load Management

Bunn, Michael Trevor
Seet, Boon-Chong
Baguley, Craig
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Doctor of Philosophy
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Auckland University of Technology

The increasing penetration of electric vehicles and distributed generation into distribution networks gives rise to higher, more volatile and bi-directional energy flows through distribution transformers. Consequently, improved distribution transformer design and monitoring approaches are required to minimise future capital expenditure and maintenance costs over the distribution transformer’s lifetime. Traditionally the determination of the health and life of a distribution transformer has relied on modelled rather than measured data, leading to inaccurate assessment of transformer health and non-optimised transformer utilisation. There are many risks associated with overloading transformers, such as increased internal heating to potentially unsafe levels. However, even without reaching unsafe levels, the potential for increased maintenance and reduced distribution transformer lifetime are justifiable causes for concern for utilities operating around a transformer’s nameplate rating. The consequence of this approach is that often distribution transformers are used at very low utilisation levels. However, transformers operate more efficiently at utilisation levels at or above 50 %.

This research presents algorithms that support the operation of distribution transformers at higher utilisation levels considering user expectations around required lifetime, manufacturer specifications and limits imposed by the Institute of Electrical and Electronics Engineers (IEEE) and the International Electrotechnical Commission (IEC) standards. Furthermore, it describes possible integration with a close monitoring system for distribution transformers, utilising fibre Bragg Grating (FBG) sensors. Such an approach can avoid wholesale replacement of existing distribution transformers and limit resource waste over the lifetime of the transformer.

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