Evaluation of vegetable ester for filling large power transformers

in recent times the new desires for a safer nonflammable, environmental acceptable and less impacting on non-renewable common resources fluid has driven many users in the research and use of alternative fluids to mineral oil. Despite the availability of other fluids the natural (from vegetable seeds) esters represent actually the best alternative to mineral insulating oils [1]. Terna as Italian Transmission System Operator in according to European Union Directive 2001/42/EC should aim at guaranteeing high levels of environmental protection, so Terna is also aware of its responsibility towards the community and has translated this into a single strategy: to find the right balance between the country's energy needs, nature conservation and the safeguarding of Italy's cultural heritage. Some other benefits are expected with the application of natural esters instead of mineral oils, in terms of reduced protection costs (simplification of firewalls erection, of fire protection system, of liquid containment pool, etc.) and as well as in terms of lower insurance premiums. On this basis Terna has started a research for the evaluation of the applicability of environmental friendly vegetable fluids in big power transformers. Present paper reports the laboratory scale experiments for testing and comparing different vegetable esters existing on international market