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Dielectric Response Analysis Characteristic of Service-Aged XLPE Cables
(2024-01-01)
Thongkong, Patchara
;
Promphanich, Wiboon
;
Udomluksananon, Patt
;
Jeenmuang, Siwakorn
;
Wiangtong, Theerayod
The main insulation used in plastic underground cables is cross-linked polyethylene (XLPE). The XLPE underground cable which has been utilized in service for a long time, has experienced various stresses, or so-called TEAM stresses. Consequently, the XLPE insulation will be degraded over time and lead to insulation properties degradation. This paper represents the dielectric response analysis technique for characterizing the insulation condition of the service-aged XLPE medium voltage underground cable. The dielectric response analysis was performed on the 22 kV XLPE underground cables that have been in service for more than 10 years and were directly buried. The dielectric response analysis measurement consists of a combination of polarization and depolarization current (PDC) measurement in the time-domain and frequency-domain spectroscopy (FDS) measurement. After that, test results were analyzed to evaluate the insulation condition and compare it to the new 22 kV underground cable. The analyzed dielectric response analysis test results will be reported in this paper.
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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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The Application of Polarization and Depolarization Current on the Large Turbo-generators
(2022-01-01)
Jeenmuang, S.
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Pannil, P.
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Mongkolsatitpong, S.
;
Trakuldit, S.
;
Wuti, V.
This paper represents the application of the polarization and depolarization current (PDC) measurement of the stator winding insulation of two large turbo-generators, which have the same rate of 50.8 MVA, and 11.5 kV. The PDC measurements were conducted on the stator winding insulation of both generators by using two different test circuits i.e., (individual) phase-to-ground insulation and interphase insulation circuits. Then, the PDC results of the two investigated generators were compared. To evaluate the phase-to-ground insulation condition of the stator winding insulation of both generators, the conventional dielectric parameters in the time domain, such as polarization index and insulation resistance, were also studied. Moreover, the PDC results in the time domain were converted into the dielectric dissipation factor in the frequency domain to allow the analyzing the phase-to-ground insulation of the stator winding of the generators. The PDC results of the phase-to-ground insulation circuits of both investigated generators illustrate the bent shape of PDC results which were affected by the influence of the stress control coating resulting in a high value of the Polarization index. Besides, the PDC results of the interphase insulation circuits of the first investigated generator illustrate the polarity reversal (or Anomalous current) of both PDC, while the second investigated generator illustrates the non-polarity reversal of both PDC. The polarity reversal of the PDC results of the interphase insulation was due to the dielectric loss of the interphase insulation is a lower influence when compared with that of phase-to-ground insulation.
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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.

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