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Subject: search.filters.subject.polarization current

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    The Response of Natural Esters when Being Under a Direct Current Electric Field for a Long Time
    (2024-01-01)
    Thungsook, Kittisak
    ;
    Manger, Rene
    ;
    Zink, Markus H.
    ;
    Kobus, Maja
    ;
    Pattanadech, Norasage
    This study examines the dielectric behavior of natural esters exposed to a DC electric field over an extended period of time. The dielectric response was investigated by using polarization and depolarization current measurements. The natural ester sample was subjected to a DC electric field of 0.1 kV/mm, 0.5 kV/mm, 1 kV/mm, 1.5 kV/mm, and 2 kV/mm, respectively. Besides, the moisture content of natural esters was also controlled using a natural method. The test results showed that after being exposed to an electric field for an extended period of time of the natural ester, different forms of charge accumulation might be found partly depending on the initial condition of the investigated natural ester.
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    Application of Polarization and Depolarization Current Measurement for Rotating Machine Insulation Analysis
    (2021-01-01)
    Pattanadech, N.
    ;
    Nimsanong, P.
    ;
    Worthong, T.
    Rotating machine is a vital asset of the power plants. For the motors and generators in service, the stator winding insulation is generally operated under thermal, electrical, ambient, and mechanical stresses. The combination of these stresses causes insulation degradation that can lead to early aging or severe damage and, finally, the failure of such machines. The failure of rotating machines may result in immense financial loss and other aspects. Polarization and depolarization current (PDC) measurement has been introduced as one of the time-domain dielectric spectroscopy test techniques applied for insulation condition testing. This paper represents the application of PDC measurement to evaluate the insulation for the stator bars/coil insulation experienced with various kinds of stresses. Moreover, the PDC field test of generators and high voltage motors used in the power plants is introduced. From the experiments, the dielectric parameters obtained from PDC measurements are clearly useful parameters to evaluate the electrical insulation of such rotating machines.
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    The Polarization and Depolarization Current Characteristics of Natural Ester Stressed by Partial Discharge
    (2020-10-25)
    Maneerat, Noppadol
    ;
    Makmork, Kawee
    ;
    Kittikhuntharadol, Yannaphol
    ;
    Suksai, Nattapat
    ;
    Chusang, Thanapat
    This paper represents the polarization and depolarization current (PDC) of the natural ester stressed by partial discharge (PD). The needle-plane electrode was used to simulate corona discharge in natural ester. Besides, the needle electrode as a high voltage electrode placed on the 8 hours natural ester impregnated pressboards and the plane electrode as a grounded electrode were used to simulate the surface discharge. To simulate the internal discharge, the plane-plane electrode inserted with various condition impregnated pressboards were experimented. PD phenomena were simulated in the natural ester container for 1, 3, and 6 months. Then the PD-stressed natural ester was used as the liquid specimen for polarization and depolarization current measurement. It was found that the PDC characteristics of natural ester undergone with various PD types were obviously different.
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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.