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Subject: search.filters.subject.DIELECTRIC RESPONSE MEASUREMENT

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    A CASE STUDY ON DIELECTRIC RESPONSE MEASUREMENT OF HIGH VOLTAGE GENERATOR INSULATION SYSTEMS
    (2023-01-01)
    Kunakorn, Anantawat
    ;
    Jeenmuang, Siwakorn
    ;
    Pattanadech, Norasage
    Dielectric response measurements (DRMs) are a non-destructive method that has long been widely employed to state the insulation condition of many power system components. Such methods can reflect the deterioration problems that occur in the insulation system of rotating machines, such as conductive contamination on the end winding surface, moisture absorption, and stress grading system deterioration. In this paper, the investigation of the DRM of the stator winding insulation of an indirect hydrogen-cooled generator rate of 211.75 MVA, 15.75 kV is presented. The DRMs are carried out using polarization and depolarization current (PDC) as well as frequency domain spectroscopy (FDS) on the stator winding insulation system. The experiments are performed on both phase-to-ground and interphase insulation. Various dielectric characteristics, which are polarization current, depolarization current and a dissipation factor are recorded and analysed. The phase-to-ground PDC results show the natural characteristic of the stress grading system as a hump occurring in the current trace. In addition, the measured PDC results are converted into a frequency window so that calculated parameters can be compared with the measured FDS test results.
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    INVESTIGATION OF STATOR WINDING INSULATION CONDITION OF MV MOTORS BASED ON DIELECTRIC RESPONSE MEASUREMENT
    (2023-01-01)
    Pattanadech, Norasage
    ;
    Jeenmuang, Siwakorn
    ;
    Dorkmai, Kritsada
    ;
    Chumpiboon, Komin
    ;
    Udomluksananon, Patt
    This paper presents an investigation of the stator winding insulation condition of medium voltage (MV) motors operated in a power plant. The investigated motors have the same voltage rate of 6.6 kV. Such motors continuously encounter various stresses during service which alter the dielectric properties of the insulation system. Thus, the dielectric response measurement (DRM) was utilized in this research to evaluate the integrity of insulation of stator winding insulation, whether the bulk insulation e.g., moisture absorption, or the surface insulation e.g., existing conductive contamination over- or even moisture adsorption along the endwiding surface. In addition, polarization and depolarization current (PDC) and frequency domain spectroscopy (FDS), as techniques based on DRM, were employed to allow the analysis in both time and frequency domains. Such techniques were performed on the whole MV motors during the shutdown for time-based maintenance, both before and after cleaning and drying for comparison purposes. The visual inspection of such motors evidences that there has considerable dust over the endwinding surface. Such motors were thus thoroughly cleaned to remove such visible dust over the surface of the endwinding. Then, the DRM test results before and after cleaning, were comparably analyzed to characterize the dielectric properties due to such contaminant. Therefore, the effect of the contaminants on the dielectric properties of the stator winding insulation system is introduced and discussed.