What are the advantages of using natural ester transformer oil compared to mineral oil?

Natural ester oil offers higher fire point, improved biodegradability, and reduced environmental impact. It can improve paper moisture management because it tends to absorb moisture, helping keep cellulose insulation drier in equilibrium, which can slow insulation aging. Many utilities use it for urban substations, indoor installations, and environmentally sensitive sites. Tradeoffs can include higher viscosity at low temperature and different oxidation behavior, so cooling design, cold climate performance, and standards compliance must be checked before selection or retrofill.