ester based transformer fluid

Fires in mineral oil-filled transformers are notoriously unforgiving, spreading very quickly and causing extensive damage, often including human casualties. Worldwide, transformer fires are reported with disconcerting frequency.

MIDEL ester transformer fluids provide the perfect solution in terms of transformer fire protection. Used and respected globally, MIDEL fluids have an impeccable fire safety record – international insurers FM Global® and Underwriters Laboratory (UL) have listed MIDEL fluids as less flammable fluids for dielectric purposes. This means they require lower fire safety measures than mineral oil.

In addition, MIDEL’s fire safe properties allow for their use in transformers inside buildings and other critical areas where mineral oil would not be acceptable.

Increased safety can also mean reduced project costs. The costs for safeguarding against the risk of fire (such as fire suppression systems) can be significantly moderated when using a fire-safe ester fluid.

The bottom line is risk mitigation. MIDEL is tested, proven and acknowledged worldwide as Best Practice; our customers specify MIDEL instead of mineral oil as a strategy against compromising safety.

MIDEL ester transformer fluids are fully and readily biodegradable and fire safe – properties not found in mineral oil. Our fluids present a much lower risk to the local environment if spillage occurs (readily biodegradable according to OECD 301 and fully biodegradable according to IEC 61039).


our range of transformer fluid

Natural ester oil -Rapeseed

MIDEL eN 1204 is a superior natural ester transformer fluid, made from renewable  rapeseed/canola oil. It delivers very effective cold weather performance and has better oxidation characteristics than soya-based natural ester fluid. The right solution for non free-breathing transformer in cooler climates. 

Natural ester oil - soybean

MIDEL eN 1215 is a versatile, fire-safe ester transformer fluid made from renewable soybean crops. Environmentally safer than mineral oil, MIDEL eN 1215 is the ideal solution for non-free breathing transformers in temperate climates. Reliable performance from an ester fluid with sound sustainability credentials.

Synthetic organic ester oil

MIDEL 7131 is the world’s leading biodegradable synthetic transformer fluid. Proven to 433kV and with a pour point of -56°C, this is a robust fluid for mainstream and the most demanding environments – including extremes of heat or cold, sub-sea, underground, offshore wind and traction applications – for both sealed and free-breathing units.