Physicochemical and Dielectric Study on Nigerian Thevetia Peruviana as a Potential Green Alternative Fluid for Transformer Cooling/Insulation

Vegetable oil has shown a promising behaviour in replacing mineral insulating oil for transformer insulation due to the environmental unfriendliness of mineral oil. However, attention was placed mostly on edible oil which may eventually lead to food competition. In this work ester from Thevetia Peruviana oil, non-edible vegetable oil was considered as alternative oil for transformer insulation. The functional groups and the fingerprints of the synthesized methyl ester from the yellow oleander oil were confirmed using Fourier Transform Infrared (FTIR) Spectrometry and the fatty acid composition was determined with Gas chromatography mass spectrometry (GC/MS). The viscosity of methyl ester and mineral oil were obtained to be 4.8 mPas and 9.8 mPas at 30 °C. The pour point of methyl ester was obtained to be 1.4 °C which could be enhanced by a pour point depressant when considering it for use in a low temperate region. The adequacy of this synthesized oil as an insulating oil was further explored by measuring the dielectric properties. The result revealed that methyl ester has a higher dielectric constant relative to mineral oil and a dielectric loss of 0.0045 at 30 °C. The dielectric strength of the oil was analysed using two-parameter Weibull plots. The characteristic breakdown strength of mineral oil and yellow oleander methyl ester was obtained to be 21.9 kV and 23.3 kV respectively. The result obtained from this work is an indication that methyl ester from the non-edible vegetable oil is a promising alternative insulating oil for oil-filled transformer insulation. Graphical Abstract