Effect of inhibitors on thermal degradation of vegetable oils

Electrical insulation system is an important part of electrical equipment with high requirements - accuracy, quality, reliability and environmental protection. In power and distribution transformers is the most common electrical insulating system oil-paper system. The liquid component of the insulation system is used as a cooling and insulating medium as well. The most commonly used liquid insulating material is a mineral oil, which has excellent electrical properties - low dissipation factor, high dielectric strength, sufficient oxidation stability etc. The current research is focused on alternative to mineral oil because mineral oils are a threat for environment in case of a leakage from the transformer. Another reason why we look for a replacement is that a mineral oil comes from a non-renewable source. The research has focused on selecting appropriate mixtures of synthetic esters and on modification of natural esters. The electrical and physical properties of these newly created oils were compared using the mineral oil. In this paper, two different of vegetable oils (rapeseed oil and sunflower oils) are tested. The aim of the paper is to show the electrical properties of sunflower oil and his lifetime curve depending on temperature and on different time of exposure. At the end of the paper, the results of the experiment are discussed and life time curves for different temperatures are calculated.