Study on the Ageing Characteristics of Persea Americana Oil as an Alternative Transformer Insulation oil

Abstract

Mineral insulation oils have been used as a liquid insulation in electrical equipment for several decades. However, mineral oil is non-biodegradable and non-renewable. It has been predicted that they may run out in the near future. There is thus an urgent need to find their alternatives. Natural, plant based insulating oils are the solution. They are non-toxic, and possess higher fire points and excellent biodegradability characteristics. Therefore, to improve fire safety of transformers and to decrease the harmful environmental impact, there is an increasing demand for these insulating liquids as transformer insulating oils. Persea americana ester (PAE), a plant based oil has high biodegradability and is renewable. PAE has shown through experiments, a likelihood of being an alternative to mineral insulation oil (MIO) because of its good physico-chemical and electrical properties, so far investigated. Since insulating oil for transformers is used over several years, it is imperative to study the ageing characteristics of proposed new insulation oils. Accelerated ageing using open beaker method with copper catalyst was carried out to predict the reliability of Persea americana oil when in operation. The ageing test was based on accelerated thermal ageing to induce the ageing mechanisms within a short period (96 and 164 hours). Results obtained for Specific Resistivity at 27°C and 90°C, Dielectric dissipation factor, Total acidity and sludge for PAE; suggest that PAE could be a potential transformer insulating liquid. For comparison, the corresponding properties of mineral insulation oil (MIO) in the same experimental conditions were also measured. The results obtained as per the IEC and ASTM specifications gives hope for new natural liquid insulation oil.