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    Polarization and Depolarization Current of Pressboard Impregnated with Natural Ester under Thermal Stress
    (2022-01-01)
    Kittikhuntharadol, Yannaphol
    ;
    Worthong, Tehneht
    ;
    Pattanadech, Norasage
    Mineral oil has long been utilized in transformers due to its low cost and suitable qualities. Alternative liquid insulations with great characteristics have recently been presented, and natural ester was considered. Pressboard is a type of cellulose insulation used for electrical insulation and mechanical support. This paper intends to study pressboard impregnated with natural ester under thermal stress. The pressboards and the natural ester were prepared for the experiment. Vacuum ovens were used for moisture elimination of materials and the impregnation process. The test specimens consisted of impregnated pressboards for 0, 8, 16, and 24 hours with thermal stress by heating at 150 degrees Celsius in a vacuum oven for 0, 30, and 90 days. Polarization and depolarization current (PDC) of the test specimens were investigated in each period by PDC-Analyser 1MOD. The test cell for PDC measurement was designed according to JIS C2111, and it was clean before the experiment. The PDC characteristics of the pressboard that had been subjected to thermal stress were discovered to be slightly different when compared with the same impregnation time of the pressboard.
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    Dielectric Properties of Natural Ester Mixed with Nanoparticles under Thermal Stress
    (2020-10-25)
    Kittikhuntharadol, Yannaphol
    ;
    Vittayakorn, Wanwilai
    ;
    Pattanadech, Norasage
    This paper aim to study of the dielectric properties of thermal stressed natural ester mixed with TiO2, and ZnO. Polarization and depolarization current (PDC) along with dielectric loss factor (tanδ) of the test specimens were investigated. The test specimens comprised of unmodified natural ester and natural ester mixed with different volume concentration, i.e., 0.01%, and 0.03% of TiO2, and ZnO. After preparing the natural ester and the natural ester nanofluid specimen, such specimens were undergone with thermal stress at 110 degree Celsius for 72 hours in vacuum oven. Then, a PDC-Analyser-1MOD was utilized for PDC measurement of the test samples. For tanδ measurement, test circuit was set-up according to IEC 60247 and the C and tanδ meter with the liquid electrode were used. From the test result, thermal stress strongly affects the PDC and tanδ characteristics of the liquid samples. Besides, natural ester mixed with 0.01% of TiO2 concentration shows the high potential dielectric liquids compared with other specimens.