Progress report on natural esters for distribution and power transformers

Natural ester seed oil based dielectric fluid is an environmentally advantaged fluid that is increasingly being used as a replacement for mineral oil and for high temperature flashpoint liquids, including silicone and R-TEMP. This report updates experience with use of the fluid over the last two years. Considerable studies have been conducted to investigate heat aging performance of cellulose, electrical contact thermal stability, dielectric strength, moisture sensitivity, and cold temperature performance. A series of reports presents a summary of work that has been completed to date and examines customer experience with the use of natural esters in real transformers. The work contains both new transformers and retro-fills in distribution and power transformers as well as step voltage regulators and switchgear.