Diagnostics of distribution class transformers

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Cselkó Richárd
Department of Electric Power Engineering

Distribution transformer is an imperative link of the distribution system without which the utility would not be able to supply electricity to consumers. Due to constantly increasing population and hence load demand, the number of distribution transformers is now continuously increasing. In the event of failure of distribution transformer, apart from the loss of capital to the utility, the consumer Suffers due to inconvenience caused by the interruption of power supply. Power supply utility also suffers due to loss of revenue for supply outage period.

This project aims to discuss about failure modes of distribution class transformers and perform different offline and online diagnostic methods to evaluate their ability to detect the most common failures on these kinds of transformers in the High Voltage Laboratory.

Nowadays we are facing a growing demand for electrical energy as well as an increasing average age of power transformers in distribution networks [1]. Due to the liberalized energy marked, electrical utilities focus on low costs. Since transformers are one of the most important and cost-intensive components of the electrical power supply, utilities try to postpone investments for replacements. As a result the average age of a transformer is increasing. Ageing of high voltage equipment typically means ageing of the insulation. Different faults are caused by different reasons, which all have different impacts on the power system If not recognized early enough, this could lead to catastrophic failures and high follow-up costs. Therefore, it is necessary, that critical defects are observed before a failure happens.

Regularly performing a range of standard electrical tests has proven an effective way to gain a reliable insight into the operating condition of your transformers and can extend their lifespan. Mechanical changes to windings, contact problems in the tap changer or at other connections, shorted windings/coils, as well as interruptions or short-circuit of parallel lines can all be diagnosed early by using conventional testing methods.


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