Natural Ester Transformer Fluids
Renewable Natural Ester for Transformer Sustainability
MIDEL eN 1204 is a rapeseed-based natural ester transformer fluid developed for environmentally conscious transformer applications. Fully biodegradable and derived from renewable sources, this fluid is especially suited for non-free-breathing transformers in colder climates and environmentally sensitive zones.

- 01 Cool Climate Ready
- 02 Sustainable
- 03 Sealed Systems
- 04 Environmentally Safe
Cold Climate Installations
With a pour point of -31°C, MIDEL eN 1204 is optimized for low-temperature environments where other natural esters may underperform.
Sustainable Grid Infrastructure
Produced from renewable vegetable oils, this fluid supports utilities in achieving sustainability targets and reducing carbon footprint.
Non Free-Breathing Transformers
Recommended for sealed system designs where oxidation stability and eco-compatibility are critical.
Eco-Sensitive Installations
A natural choice for installations near waterways, conservation areas, or populated zones where environmental stewardship is essential.
Features & Functionality

Natural ester fluids are derived from vegetable oils, making them a renewable and environmentally responsible alternative to mineral oil. They are readily biodegradable, significantly reducing environmental risk in the event of a leak or spill—especially important for transformers installed in sensitive or populated areas.

With a high fire point (typically >300°C), natural esters are classified as “K-class” fire-safe fluids. This drastically reduces the risk of transformer fires, improving safety in high-risk locations such as tunnels, buildings, or bushfire-prone areas, and can reduce the need for costly fire suppression systems.

Natural esters are highly hygroscopic, absorbing and retaining moisture without compromising insulation performance. This reduces the risk of paper insulation degradation and prolongs transformer life, especially in non-free-breathing transformer designs where moisture management is critical.

Unlike soy-based alternatives, MIDEL eN 1204 (rapeseed-based) has a pour point of -31°C, making it well-suited for installations in colder climates. This allows utilities and OEMs to specify natural ester fluids with confidence, even in regions with extreme weather conditions.
Functionality & Options
-
Derived from renewable vegetable oils, MIDEL eN 1204 offers a low environmental impact and is readily biodegradable. Ideal for installations in environmentally sensitive locations.
-
With a fire point above 300°C, natural esters are classified as K-class fire-safe fluids, enabling safer transformer designs without the need for additional fire suppression systems.
-
Natural esters are hygroscopic, meaning they absorb and retain moisture. This helps protect the paper insulation, slow ageing, and extend transformer service life.
-
MIDEL eN 1204 (rapeseed-based) has a pour point of -31°C, outperforming soy-based esters and making it more suitable for colder installation conditions.
Key Technical Specifications
-
Suitable for power transformers up to 400 kV
-
Pour point: -31°C (MIDEL eN 1204)
-
Fire point: >300°C (K-class fluid)
-
Biodegradability: Readily biodegradable
-
Viscosity (40°C): Approx. 35–40 mm²/s
-
Moisture saturation limit: >1000 ppm
-
Dielectric strength: >65 kV (ASTM D1816)
-
Meets IEC 61099 and IEEE C57.147 standards
-
Produced from renewable rapeseed oil
-
Compatible with sealed, non-breathing transformer designs
Our Projects featuring Insulect Ester Fluids
Explore our project highlights to see where Insulects Ester Fluids. For tailored advice on whether this solution suits your network, please connect with our team here.
Where you'll find Insulect Ester Fluids
You'll find Insulect-supplied Ester Fluids products across Australia and New Zealand.

Why Choose Insulect for Natural Ester Fluids
Insulect provides Australian utilities and energy providers with world-class Natural Ester Fluids backed by deep industry expertise, local support, and future-ready technology.
Natural esters like MIDEL eN 1204 reduce reliance on fossil fuels and minimize ecological risk.
The low pour point ensures consistent performance in harsh winter climates.
Natural esters align with modern ESG standards, making them the fluid of choice for utilities committed to a greener grid.
Services & Support
Insulect offers comprehensive services and support for the products we manufacture and specialise in, enhancing value for local utilities, major energy users, equipment manufacturers, and service operators.
Our local technical team provides exceptional support and expertise, ensuring quick response times and personalised service to tackle any challenges that may arise during project execution.
Our team utilises advanced technology and industry knowledge to develop innovative and efficient high voltage switchgear solutions, customised to fit the unique requirements of each project.
We facilitate smooth procurement and logistics processes by sourcing from trusted, proven partners and coordinating timely deliveries, ensuring projects remain on schedule and within budget.
We are able to oversee every phase from concept to completion, providing comprehensive solutions that simplify complex projects and ensure successful outcomes.