Effect of temperature on dielectric loss factor of biodegradable transformer oil

This paper is aimed at the investigation of the effect of temperature on the dielectric dissipation factor of fresh and wetted natural ester oil. It is shown that tgδ increases with temperature; this increase is weak at the low temperature, in the range 20°C to 90°C. An increase in temperature from the ambient to almost 80°C causes a threefold increase in loss factor. For temperatures higher than 110°C, a noticeable increase in the value of tgδ is observed; this increase can reach two orders of magnitude. Also the presence of dissolved water in natural ester oil increases its loss factor.