New insulating fluids for transformers based on biodegradable high oleic vegetable oil and ester fluid

The development of new insulating materials is guided by multiple parameters, as new environmental requirements and other safety or economical considerations. Therefore the transformer manufacturers have to face new specifications linked with these requirements. As these requirements are different from country to country, we can expect different approaches for the different markets. ISO and IEC have issued guides to consider these aspects. As ester or vegetable fluids are more expensive in comparison with mineral oil, it is important to optimize the design of the windings in order to take all the benefits of such modern fluids, beside the fire behavior and the other environmental aspects (toxicity, water pollution, waste treatment, etc). The use of ester fluids is common now, and much experience has been accumulated during the last decade. The vegetable oil is a new candidate to replace mineral oils in the future. Therefore this report is mostly dedicated to this new technology which represents a promising market. The development of a biodegradable electrical insulating fluid from high oleic vegetable oil sources is described. This type of oil was selected due to the inherent higher stability of high oleic oils over commercial grade oils. However, the selected oil had to be further purified to improve electrical properties, and special additives were used to enhance the oxidative stability in the environment of electrical equipment. The electrical equipment specifically targeted for immediate use was distribution transformers