Electrical and physicochemical properties of mineral and vegetable oils mixtures

This work is devoted to the study of electrical and physicochemical properties of naphthenic mineral oil and natural ester olive oil mixtures; seven mixtures with different mineral oil/vegetable oil ratios are considered. The main investigated properties are breakdown voltage, density and charging current response. All the physicochemical properties measurements are achieved in respect with IEC standards. DC charging currents are measured thanks to a programmable electrometer (Keithley 617 type) for long field application duration. The main task concerns the search of the best mixture or at least the ratios that are in accordance with international standards requirements to be used in transformers with comparable properties as that of new mineral oil. The advantages of each of them will be discussed in relation with the main required properties.