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    Polarization and Depolarization Current Characteristics of Natural Ester Impregnated Pressboards with Different Periods of Impregnation
    (2020-10-25)
    Maneerot, Sakda
    ;
    Siriworachanyadee, Jompatara
    ;
    Likhitsupin, Wit
    ;
    Likhitsupin, Suwapich
    ;
    Srinangyam, Chissanupong
    This paper represents the polarization and depolarization current (PDC) characteristics of natural ester impregnated pressboards with different impregnation period. The pressboard specimen were prepared as a rectangular shape (the length and the width are 120 mm as well) and thickness dimension of the pressboard in the experiment was approximately 1.6 mm. The pressboards were dried up in the vacuum oven with temperature at 80°C for 12 hours under 200 mbar pressure. In addition, these pressboards were divided into 3 groups according to the impregnation periods. The 1st group, the pressboard was non-impregnated with natural ester. The 2nd and 3rd group, the pressboards were impregnated at 60°C for 8 and 16 hours, respectively, under 200 mbar pressure-controlled condition. The plane-plane electrodes inserted with the specified number of the pressboard specimens were prepared. These electrodes were installed in the test cell filled with the natural ester. A 24 kV AC Voltage was applied to the test cell for 3 months. At the end of the first month, half of the pressboard samples was token from the test cells. Then, the PDC characteristics of these natural ester impregnated pressboards were investigated. At the end of the third month, another half of the pressboard samples was token from the test cells to perform PDC measurement also. It was found that the PDC values of the pressboards with longer period impregnation process were lower than these of the pressboards with longer period impregnation process. Besides, the PDC values of the pressboards experienced with longer electric field stress period (3 months) were higher than these of the pressboards experienced with shorter electric field stress period (1 month).
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    Experiences in nonconventional partial discharge measurement for gas-insulated substation in Thailand
    (2020-01-01)
    Nganpitak, Tritod
    ;
    Kunakorn, Anantawat
    ;
    Klienhom, Sitthisak
    ;
    Likhitsupin, Suwapich
    ;
    Jariyawichai, Parinya
    Nowadays, nonconventional partial discharge (PD) measurement has become essential for diagnosis the high-voltage insulation condition. The nonconventional PD measurement not only uses for periodic assessment but also uses for commissioning test after transportation and installation. This paper focuses on nonconventional PD test techniques using Ultra-high frequency (UHF) sensors, acoustic sensors and light detection sensors for gas-insulated substation (GIS) commissioning test. Fundamental defects found in GIS: (1) Hopping particles (2) Fixed protrusions (3) Floating potential and (4) Voids are described. Then, explanation about how to detect such defects by using UHF, acoustic and optical methods. Afterwards, PD commissioning tests were performed with three 230 kV electricity generating authority Thailand (EGAT) GISs, i.e., Phayao EGAT GIS, Lamphun 2 EGAT GIS and North Bangkok EGAT GIS. The PD signals due to hopping particle were found by using UHF sensors at Phayao and North Bangkok EGAT GISs. The acoustic PD test technique was used in Phayao EGAT GIS to locate such particles. In case of Lamphun 2 EGAT GIS, by using UHF measurement, PD signals were found due to tracking caused by flashover on the cone insulation surface. Later, light detection sensors were used to detect the PD location. As a result of studies, its clearly guarantee the powerful accuracy and efficiency of nonconventional PD measurement by the combination of UHF and acoustic technique including light detection sensors.