AC Breakdown and Resistivity of Natural Ester Based Nanofluids

In this paper, AC breakdown including resistivity of natural ester and natural ester mixed with nanoparticles were studied. Two types of nanoparticles i.e. Barium titanate (BaTiO3) and Titanium dioxide (TiO2) which have their diameter less than 100 nm were used in experiment. For the nanofluid samples, three concentration of nanoparticles including 0.01%, 0.03% and 0.05% were prepared in five processes. Firstly, the natural ester mixed was with 0.01%, 0.03% and 0.05% of volume fraction of nanoparticles. Second, a magnetic stirrer was used to diffuse them evenly over the liquid later, ultrasonic dispersion was also used to ensure that the prepared nanofluids were homogeneous. Then, the nanofluid liquid was heated at 80 degree Celsius in vacuum oven for 15 hours. Finally, this liquid was dispersed by using magnetic stirrer again. Besides, the mixed liquid sample was heated at 110, and 130 degree Celsius for 72 hours to simulated thermal stress. To measure the AC breakdown voltage, a dielectric breakdown testing device was used. The test circuit was set up according to ASTM D1816. The gap distance between electrode was set at 2.0 mm. Furthermore, the test cell for liquid insulation testing (Model DAC-OBE-2: SOKEN) was used for polarization and depolarization current (PDC) experiment. The PDC test result was then used to calculated the resistivity of the liquid samples. The test results show that the AC breakdown voltages of the natural ester mixed with nanoparticles is higher than unmodified natural ester. Additionally, Barium titanate nanoparticles and Titanium dioxide nanoparticles enhance the breakdown strength and the resistivity of the ester nanofluid tested. According to the results, it concluded that nanoparticles were an good alternative to enhance the dielectric properties of natural ester for dielectric application.