Electrical properties of natural oils and methyl esters of their constitutive fatty acids

This paper deals with the analysis of prospective environmentally compatible electrical insulating fluids for electrical engineering in relation to their chemical structure. The paper starts with the overview of the current state of the art and of the latest trends in the use of synthetic and biodegradable natural oils. In the experimental part, rapeseed oil, sunflower oil, soybean oil, methyl palmitate, methyl laurate, methyl oleate and methyl stearate were studied. Dielectric properties were measured using precision LRC meters Agilent 4284A and 4980A including dielectric liquid test fixture Agilent 16452A and also by the Novocontrol Alpha-A analyzer. Electrical properties are presented in the frequency range 1 x 10(-2) - 1 x 10(7) Hz range in the temperature interval -20 degrees C to 80 degrees C. The paper goes on with the study of the suitability of individual oils for lower temperature, including the impact of the chemical structure and formulation on electrical properties.