Abstract: The success of any electrical system lies in its insulating system performance. Petroleum based mineral oils are the generally used fluids for electrical insulation and heat transfer. But they are non-biodegradable. Vegetable oils obtained from seeds, flowers and vegetables are biodegradable, non -toxic, environmental friendly and benign to aquatic or terrestrial. The objective of this paper is to analyse the breakdown voltage and physical viscosity, flash point and fire point of sunflower oil, palm oil and mineral oil with and without moisture in them at different gap distances.

Keywords: HV (high voltage), BD (breakdown), Breakdown strength , Vegetable oils, Flash point and fire point.