Impact of oils degradation on the cooling capacity of power transformers

Published in 2015

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Summary

Many transformers around the world are serving close to or beyond their designed life. Faced with the growing demand for electricity, the management of the aging transformer overload has become a very important issue within utilities. With increasing loads, the risks of thermal degradation are also increased with potential explosion in extreme cases. Core and coil losses in operating transformers generate significant internal heat that, unless dissipated, can increase the rate of aging of the insulation system and shorten the life of the insulation system. In this contribution, the impact of aging on the viscosity of mineral oils is reported. A thermo-fluid numerical study involving the cooling capacity of oil aged at different levels using a 2D axisymmetric model developed with the commercial software COMSOL Multiphysics, is reported. The results show a correlation between the aging indicators and the viscosity. This contribution also provides evidence that the chemical composition of fluid and the oil decay products are also contributing factors to temperature rise and an increase of hot spots in the transformers windings.