Ageing Characteristics of Alkali Neutralized Neem oil for Liquid Insulation

Mineral insulating oil is used in transformers and electrical equipments as an insulant and coolant. After prolonged usage, these oils deteriorate and progressively develop sludge and need to be replaced. Disposal of the waste insulating oil leads to contamination of natural resources. There is a need to find an alternative source for insulating oils. This study explores the possibility of using alternative insulating oils that are safe to dispose off after use. Experiments are carried out using non-edible vegetable oil extracted from neem seeds as a source of sustainable and environment-friendly insulating oil. Characteristics such as viscosity, acidity, electric strength, dielectric dissipation factor, resistivity, flash point and fire point have been evaluated. The results of crude neem oil are compared to the acceptable limits of IEC 62770 - 2013 to understand the suitability of crude neem oil. It is found that crude neem oil has acceptable values with respect to density, viscosity, electric strength, flash point and fire point values and poor performance with respect to total acidity dielectric dissipation factor, specific resistance. Hence, the crude neem oil is processed by alkali neutralization followed by vacuum filtration to alter the performance of crude neem oil. The alkali neutralized neem oil shows better performance with respect to acidity, dielectric dissipation factor, specific resistance, electric strength parameters and flash point and fire point values. Further, the processed oil is subjected to ageing conditions to study the long term performance of the alkali neutralized neem oil.