Study on the cooling capacity of alternative liquids in power transformers

This work focuses on the thermal behavior of natural esters on power transformers. For this purpose a model of the windings is presented. These are considered as a set of rectangular blocks representing the cross section of the different turns of copper. The model is implemented in a finite element method tool and it is considered as a two-dimensional problem. It serves to study how the dielectric liquid flows between the channels of a disc-type power transformer. The results of this study are compared to the thermal behavior of the conventional mineral oil. It seems that natural esters produce a positive effect in the solid insulation. It is also shown that windings suffer higher temperatures in the case of mineral oil, this leading to a faster speed on insulation deterioration. On the other hand, a wrong design of the horizontal channel size can lead to hot-spots in natural ester-cooled transformers.