Natural and Synthetic Ester Liquids as alternative to mineral oil for power transformers

The combination of a solid and a liquid insulation is the most frequently used insulating system in high voltage transformers, where components have to be insulated and loss heat has to be dissipated. The requirements on the liquid part of the insulating system are not only the electric and dielectric performance but also the performance regarding environmental requirements and dehydration capability as well as low inflammability. The contribution presents a comparison of the performance of natural and synthetic ester as an alternative to mineral oil.