Sustainable Transformer Project

The purpose of this project is to conduct the studies and tests required to confirm the technical feasibility and economic impact of replacing the mineral oil currently used (at voltage levels of 400kV) as an insulating and cooling medium in transformers for a biodegradable vegetable oil that is more sustainable and more environmentally friendly. Transformer mineral oil is highly polluting, and is classified as a hazardous and highly flammable substance.


Factory tests have been conducted on a conventional-design transformer (with modifications, taking into account the lowest possible financial impact) using vegetable oil and synthetic oil, both biodegradable and more environmentally friendly. The results have been positive, proving that these oils can be used in power transformers, as their biodegradation rate is 97% after 21 days (in the case of mineral oil it is just 30%).

Shortly, a three-phase transformer will be installed and connected to the transmission grid, which will have mineral, vegetable and synthetic oil in each of its phases, in such a way that it will be possible to test and compare the behaviour of each phase under real conditions.


This project is underway. It began in November 2015 and is scheduled for completion in 2019.

Benefits/Cost reduction:

The use of a sustainable transformer offers a series of advantages, mainly due to its biodegradable nature and its low flashpoint.

Financially it is also an advantage, despite the higher cost associated with biodegradable oil and the modifications that must be made to the transformer, as the cost of waste management is reduced and construction needs in new facilities, such as the waterproofing of containment pits and vertical firewalls, are eliminated, without even considering the possible reduction of fire risk premiums and fines for spillages in the event of accidents. In addition, the degradation of the insulation decreases due to the higher heat resistance of the oil, whereby it is estimated that the useful life of the transformer would increase.

It is also estimated that a transformer that is completely redesigned to use biodegradable oil would see its dielectric loss factor reduced by up to 19% compared to a conventional unit.

Lastly, if the field tests are satisfactory, the convenience of replacing the mineral oil (30,000 tonnes) in transformers would be studied.