Evaluation of Loss Factor of Mineral Oil and Alternative Fluids with Temperature Normalization

This paper proposes the evaluation of loss factor of mineral oil and alternative fluids the natural ester (FR3) with temperature normalization. The oil samples (i.e., mineral oil, natural ester, and palm oil) were prepared for experiments. The oil samples were dried at 70 °C under 200 mbar in the controlled temperature oven and then cooled down to ambient temperature. The moisture contents of the oil samples were measured according to ASTM D1533. The test cell, according to IEC61620, was employed in these measurements. The polarization currents, ipol(t), of such oil samples under electric field stress of 0.2 kV/mm with a temperature range from 30 to 70 °C were measured, The test results are summarized in this paper. The step response measurement results were analyzed for conductivities, permittivity, and loss factor value. It was found that increasing temperature causes increasing conductivities but decreasing permittivity of oil samples.