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    AC Breakdown and Resistivity of Natural Ester Based Nanofluids
    (2020-10-25)
    Maneerat, Noppadol
    ;
    Makmork, Kawee
    ;
    Kittikhuntharadol, Yannaphol
    ;
    Suksai, Nattapat
    ;
    Chusang, Thanapat
    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.
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    Dielectric properties of mineral oil compared with natural ester
    (2017-11-29)
    Jariyanurat, K.
    ;
    Nimsanong, P.
    ;
    Chaisiri, P.
    ;
    Maneerot, S.
    ;
    Kitcharoen, P.
    In this paper, dielectric properties of the mineral oil, ELECTROL A, and the natural ester, FR3, are comparatively investigated. AC breakdown voltages, dielectric dissipation factor, relative permittivity, partial discharge inception voltage and partial discharge of the mineral oil and of the natural ester are tested. In order to verify the capability in practical use of the mineral oil and the natural ester for transformer insulation systems, the impregnation of such liquids with pressboard insulation is performed. The impregnated pressboards are tested in the laboratory to measure the AC breakdown voltages. It is found that the natural ester shows superior dielectric properties to the mineral oil except the dielectric dissipation factor.
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    Electrical characteristics of natural ester based nanofluid
    (2017-10-19)
    Potivejkul, S.
    ;
    Jariyanurat, K.
    ;
    Pattanadech, N.
    ;
    Wattakapaiboon, W.
    In this paper, the dielectric properties of natural ester based nanofluids were investigated. This research represents the improvement of the electrical properties, AC breakdown and negative lightning impulse breakdown strength, of the natural ester (FR3) by amalgamation with nanoparticles. Two types of nanoparticles i.e., Titanium dioxide (TiO2) and Zinc Oxide (ZnO), with a mean diameter of less than 100 nm were used in this experiment. The nanofluid samples, a natural ester merged with nanoparticles, were prepared in three steps. First, the natural ester was divided into four groups. The first group was merged with 0.01% concentration of TiO2 and the second group was merged with 0.03% concentration of TiO2. The third group was merged with 0.01% concentration of ZnO and the fourth group was merged with 0.03% concentration of ZnO. Second, the nanofluid samples were dispersed using a magnetic stirrer. Finally, the ultrasonic dispersant technique was applied to the prepared nanofluids to be homogeneity. To measure AC breakdown voltage of the natural ester based nanofluids, the oil breakdown tester was employed and the testing experiment was performed according to IEC 60156. In addition, the negative lightning impulse breakdown characteristic of the natural ester based nanofluid was investigated with the needle-sphere electrodes in accordance with IEC 60897. A tungsten needle with tip radius of 40m was utilized as the high voltage electrode and the 13 mm diameter brass sphere was used as the grounded electrode. The gap distance was fixed as 15 mm. The test results showed that the AC breakdown property of the modified liquids was clearly influenced by the type of nanoparticles added. The AC breakdown voltage of the natural ester with nanopaticles was slightly higher than that of the unmodified natural ester. Additionally, both TiO2 and ZnO nanoparticles demonstrated their ability to increase negative impulse breakdown voltage of the nanofluids. These tests indicated that such nanoparticles have good potential to be used with natural ester to improve the dielectric properties.