Reduced environmental impact and improved safety and performance of power transformers with natural ester dielectric insulating fluids

Natural ester fluids may be used in new transformers as well as to retrofill existing units in order to improve their performance and reliability. Designing or retrofilling power transformers with natural ester fluids requires, however, to account for a number of significant differences in properties, characteristics, and material parameters between natural ester fluids and mineral oil in order to obtain the desired performance (thermally and dielectrically). This paper gives a comprehensive review of natural ester fluids main properties and associated values when it comes to environmental impact, fire resistance and overall performance of transformers filled with such fluids. The key fluid characteristics impacting the design of power transformers are also highlighted.