Biodegradable oil transformer

Progress in the ultra-high voltage range

Vegetable oil for a sustainable energy supply

Transformers use high-quality mineral oil as an insulating fluid and as a coolant. However, vegetable oil also has the required insulating properties. As a renewable, carbon-neutral and biodegradable resource, vegetable oil has environmental benefits and a lower fire load.

In addition, there are also benefits associated with the use of vegetable oil-filled transformers in water reserves. Since vegetable oil is a natural, biodegradable resource that is not hazardous to waters, these transformers can also easily be used in water reserves and flood plains. Transformers using mineral oil, in contrast, must fulfil very stringent special building restrictions. Another benefit of vegetable oil-filled transformers: due to the vegetable oil's high fire point they can also be installed in areas with extended fire regulations, for example in residential areas.

Transformers with vegetable oil-based insulation are becoming increasingly significant. This technology marks an important step towards future-proofing the grid infrastructure. At present, the technology is still at the research and development stage. However, the long-term objective is to roll it out widely.

Building the energy supply of the future

Thinking ahead and developing innovative solutions is key in order to ensure a secure transmission system. The new transformer installed by TransnetBW at its Bruchsal-Kändelweg substation, the first one in the ultra-high voltage range operating with vegetable oil, marks an important step towards a sustainable future for the energy industry.

Around 96 tons of vegetable oil

are contained within the transformer.

The long-term objective is to make the use of vegetable oil-based insulating fluid profitable enough for general use, not just for water conservation and special fire protection areas. TransnetBW uses this pilot project to explore how conventional substances such as mineral oil can eventually be substituted.

The vegetable oil-filled transformer commissioned in 2014 has already delivered important insights in terms of durability, cooling performance, mechanical performance and lubricating properties. The transformer will continue to help in developing the solutions of the future. Current research is looking into how vegetable oils from different plants can be mixed, for example.


How does TransnetBW use innovations to contribute to the energy supply of tomorrow? How do we meet demand for a more flexible, high-performing grid for the energy transition? By carrying out pilot and model projects as well as developing new technologies and processes in order to work towards a reliable energy supply in the future. 

Read more about our innovative projects under “Innovation – fit for the future”.