Enhancement of dielectric properties of Baobab Oil and Mongongo Oil using cost-effective additive for power transformer insulating fluids

This work aims to determine the applicability of Natural Esters (NE) like Baobab Oil (BAO) and Mongongo Oil (MGO) in power transformers. The dielectric property of Kerosene (KER) is utilized to decrease the viscosity of natural esters to promote better oil circulation in transformer tanks. Kerosene, being non-volatile and a good lubricant, protects alkali metals from oxidation/corrosion and its miscible property is useful as an oil thinner. The blending compositions used here are 1% KER:99% NE, 5% KER:95% NE and 10% KER:90% NE and the blends are subjected to dielectric testing using IEC (International Electrotechnical Commission) and ASTM (American Society for Testing and Materials) standards. Favourable temperature effects are observed with an improvement of 16% in breakdown strength and 61.9% reduction in kinematic viscosity for BAO while an improvement of 24% in breakdown strength and 56.4% reduction in kinematic viscosity are observed for MGO at 10% KER addition without affecting the dielectric performance of NE. In fact, temperature has a strong positive linear correlation with breakdown voltage and an equally strong negative linear correlation with viscosity for natural esters. Based on the results, kerosene is a promising vapour drying additive, and it is therefore recommended as a cost-effective additive to reduce oil viscosity and to minimize the amount of water saturation.