Transformer oil (also called insulating oil or dielectric fluid) serves two functions in power transformers: electrical insulation between live components, and heat transfer (cooling) to dissipate heat generated by core and winding losses. Without adequate oil, transformers overheat, insulation degrades, and lifespan is dramatically reduced.

Uninhibited (Class I) mineral transformer oil contains no antioxidant additive — it relies on the natural stability of the base oil. Inhibited (Class II) oil contains DBPC (di-tert-butyl-para-cresol) antioxidant, which significantly extends oxidation resistance and service life. IEC 60296 Class II (inhibited) is now preferred for most new transformer fills.

Yes, with proper retrofilling procedures. Natural ester fluid is compatible with most transformer materials and can replace mineral oil in existing transformers. A complete drain, flush, and refill is required — simple top-up blending is not recommended as it changes the fluid properties. Interion can supply natural ester fluid and advise on the retrofilling process.

Interion supplies transformer oil from 1 drum (209L) upward. IBC totes (1,000L) and bulk tanker delivery are available for large transformer fills or utilities with multiple units. Minimum order for bulk tanker delivery is typically 3,000L.

Interion provides Certificate of Analysis (CoA) confirming key parameters (dielectric strength, moisture, acidity, colour, viscosity) for all new transformer oil supplied. For in-service oil sampling and dissolved gas analysis (DGA), we can refer you to accredited laboratories in Singapore.