Natural ester fluid: The transformer design perspective

This paper presents the perspective of employ natural ester fluid to high voltage and high power transformers. Some studies that have been done in the literature about the dielectric characteristics of natural ester fluid point to some differences, mainly in streamer propagation and long gap distance tests, when compared to mineral oil. However, all of the tests previous done, in this issue, were based on laboratory controlled conditions. This study presents the experimental results for two prototype power transformers in the voltage class of 69 kV and 245 kV, manufactured and electrically stressed to their limits in natural ester fluid. The results address to some differences in the dielectric characteristics of natural ester fluid, mainly in the presence of non-uniform electric field and long gap distances.