Temperature Dependence of Relative Permittivity and Dielectric Dissipation Factor of Nano-modified Mineral Oil for Use as Insulating Liquids in Transformers

The operational reliability of power transformers is primarily determined by the dielectric properties of the insulating liquid used. The dielectric properties of insulating oil can be expressed mainly concerning the relative permittivity and dissipation factor. This paper presents the effect of nanoparticles and temperature on the dielectric properties (relative permittivity and dissipation factor) of pure mineral oil as well as mineral oil-based nanofluids. Nanoparticles used in the study are Fe2O3, TiO2, and SiO2. A 0.02 weight% nanoparticle concentration is used to prepare three individual nanofluid samples using the two-step method with mineral oil used as base oil. The PE-ORDF-2 model consisting of a heating chamber with oil cell is used to vary the temperature of oils. The oil cell with three-electrode system and dissipation factor Bridge is used to determine relative permittivity and dielectric dissipation factor of oils for the temperature range 20 degrees C-80 degrees C at an interval of 20 degrees C according to the IEC60247 standard. The results show that the nanoparticles additions enhance the dielectric characteristics of oils whereas the temperature deteriorates them. From the results, it has been found that Fe2O3 nanofluid possesses higher relative permittivity among all the insulating liquids tested, moreover SiO2 nanofluid gives a minimum value of dissipation factor and has a negligible effect of temperature on it.