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Author: search.filters.author.Methavithit, WinaiSubject: search.filters.subject.polarization and depolarization current

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    Dielectric Response Analysis on Artificial ZnO Surge Arrester Degradation Using Polarization and Depolarization Current Based Method
    (2024-01-01)
    Chuayin, Chaitawat
    ;
    Pattanadech, Norasage
    ;
    Zinck, Matthieu
    ;
    Methavithit, Winai
    ;
    Suksagoolpanya, Suthat
    This paper presents an alternative method to investigate the problems of surge arrester based on dielectric response analysis. The study is made using a 21-kV, 25-kA station class surge arrester to be test specimens, the former Zinc Oxide (ZnO) varistors inside were removed and replaced with artificial degraded ZnO varistors (impulse ageing, tracking problems, moisture ageing under wet and dry condition and cracking ZnO varistors). The experiments are carried out by Polarization and Depolarization Current (PDC) measurement. The test result analyses were proposed in terms of both the time domain and frequency domain. The measurement results show significant differences in dielectric response characteristics between healthy surge arresters and aged surge arresters. In addition, the dielectric response analysis tends to characterise the problems of surge arrester i.e., conduction problems and polarization problems which will be further discussed in this paper.
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    Application of Dielectric Spectroscopy Analysis to Identify Unhealthy Surge Arrester by Using PDC Measurement Technique
    (2024-01-01)
    Chuayin, Chaitawat
    ;
    Pattanadech, Norasage
    ;
    Zinck, Matthieu
    ;
    Suksagoolpanya, Suthat
    ;
    Methavithit, Winai
    At present, power grid asset management is becoming a topic of greater interest, as is the condition-based diagnosis of surge arresters to ensure power supply reliability on medium and high voltage networks. Extensive studies on failure mode and arrester forensics have been conducted and are continuing, investigating with various techniques, to predict and investigate their failures. This paper presents the investigation of dielectric spectroscopy of 21-kV MV surge arresters to identify unhealthy problems using Polarization and Depolarization current (known as PDC) measurement techniques, four artificial problems (which consist of lightning, cracking, moisture ingressive, and tracking problems) were simulated on surge arresters. With the PDC measurement, it is allowed to be interpreted in both the time domain and frequency domain. The dielectric parameters will be further presented and compared. The significant relationship of dielectric response characteristics is validated by test results and is highlighted in detail in this paper. Finally, an alternative invasive offline measurement technique is proposed for surge arrester failure detection.
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    Polarization and Depolarization Current Characteristics of Thermally Stressed Stator Coils
    (2020-10-25)
    Thungsook, Kittisak
    ;
    Phumipunepon, Natnaree
    ;
    Worthong, Tehneht
    ;
    Methavithit, Winai
    ;
    Vittayakorn, Wanwilai
    When the motor is exposed to thermal stress more than its limit, its insulation characteristic degrades and/or deteriorate. This paper presents the characteristic of stator coils under thermal stress by analyzing the polarization and depolarization current (PDC) characteristics. This research used a slot part of stator coils, which were obtained from a synchronous motor rated 6.6 kV with class F (155°C) insulation. Twelve test samples of motor stator coils were divided into four groups depending on the stress temperature levels, 100°C, 140°C, 180°C, and 220°C. Each specimen was heated at the specified temperature for four cycles (6 hours per cycle). To analyze the insulation characteristic of the tested specimen, PDC measurement was performed. It was found that the PDC magnitude decreased related to the number of thermal cycles and temperature levels, as described in this paper.