Investigation of the suitability of commercially available bio-oils as insulating liquid

This paper deals with investigations on usability of commercially available bio-oils as insulating liquid. The bio-oils investigated are those that are "in general not hazardous to water" according to German General Administrative Regulation on the Classification of Substances Hazardous to Waters. The oils tested by us meeting this criteria are predominantly biodegradable hydraulic fluids of low viscosity. Besides the ecological advantages, these oils have excellent resistance to ageing, sound fluidity, low pour point and high flash point. In order to explore possible field of application of bio-oils as insulating material, dielectric tests according to IEC 156 and IEC 247 have been carried out. Tests included measurement of AC breakdown strength as well as dielectric dissipation factor tans, permittivity epsilon(r) and specific DC resistance rho. Obtained results are compared to the electrical properties of inhibited rape-seed oil RAPSOL T, which is suitable as transformer oil substitute based on our earlier reported investigations [1, 2]. This work has led to identification of a commercially available bio-oil whose electrical characteristics are equal or even better than that of RAPSOL T.