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The Effect of Surface Leakage Current on Frequency Domain Spectroscopy of 22 kV OIP Bushing
(2024-01-01)
Rojanasunan, Warisanan
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Chumpiboon, Komin
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Udomluksananon, Patt
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Jeenmuang, Siwakorn
;
Chancharoensook, Phop
In this paper the dielectric response in frequency domain or frequency domain spectroscopy (FDS) is used to assess the effect of surface leakage current both from high voltage side and ground side on the FDS results of OIP bushings. The test object in this paper is a 22 kV OIP bushing which is out of service. The surface leakage current can be simulated using the copper tape as a bandage around the bushing core in several locations. From the FDS results, several parameters i.e., dissipation factor, capacitance, and capacitance ratio together with frequency scanning of capacitance and dissipation factor from many cases were investigated to get the fundamental knowledge of how to interpret the FDS result of OIP bushing.
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The Effect of Insulating Oil Conditions in Transformer Bushing on Dielectric Response Analysis
(2024-01-01)
Srisub, Chanatip
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Maneerat, Noppadol
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Rojanasunan, Warisanan
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Buranaaudsawakul, Techatat
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Pannil, Pittaya
The bushing is one of the important parts of a transformer. Once the transformer is operated; each transformer part including its bushing starts the degradation mechanism. In some cases, the dielectric strength degradation of the bushing can lead to severe consequences. Thus, the study and diagnosis of the bushing conditions are important. This study aims to investigate the characteristics of the oil-impregnated pressboard bushing under various oil conditions by filling the new mineral oil with a controlled moisture content and letting it reach an equilibrium state to examine the dielectric response of such bushing. To determine the dielectric characteristics of the investigated bushing, A Frequency Domain Spectroscopy (FDS) device was utilized. In the experiment, the dissipation factor, capacitance, and current measurement of the bushing with different water content level were measured. The bushing test object was tested with the frequency range of 1 mHz -1 kHz. The effect of moisture clearly influenced the low-frequency ranges of the FDS. The result will be discussed in the paper.
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The Time Domain Dielectric Response of 138 kV and 550 kV OIP Bushing
(2024-01-01)
Yamsiri, Thummanoon
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Bunlaksananusorn, Chanin
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Suksawat, Dusit
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Rojanasunan, Warisanan
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Jeenmuang, Siwakorn
In this paper the dielectric response in time domain which is polarization and depolarization current (PDC) measurement is applied to assess the global condition of OIP bushings. The bushings in this paper are five 138 kV OIP bushings and three 550 kV OIP bushings which are out of service already. From the PDC results, capacitance and current trends of both voltage levels were investigated individually. PDC results in this paper can be useful data for further analysis and diagnostic.
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Partial Discharge Testing on MV Motor - Case Study
(2023-01-01)
Jeenmuang, Siwakorn
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Rojanasunan, Warisanan
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Dorkmai, Kritsada
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Chumpiboon, Komin
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Udomluksananon, Patt
A failure of a medium voltage (MV) motor during its operation could force an outage of the power plant and also lead to a loss of cost. Hence, the method to ensure the insulation quality of such a motor is needed. Partial discharge (PD) testing is one of the effective methods used to determine the defect and evaluate the integrity of the machine insulation. This paper presents the application of off-line PD testing on MV motors. In the experiment, the PD test instrument conforming to standard IEC 60270 was used as a charge-based measurement. Moreover, during the PD testing, an acoustic imaging camera was employed as an alternative technique for locating the PD sources in the stator winding part. Once PD takes place, it can generate the pressure acoustic wave that propagates surrounding the PD source. Thus, the PD source in the area of endwinding can be located by this technique. From the charge-based PD test results, the phase-resolved PD (PRPD) pattern was considered to identify the type of PD source. It was found that almost MV motors tested have delamination in the bulk insulation. In some cases, the PRPD pattern exhibits the discharge in the area of the overlap region between the semiconductive and stress grading coating in the slot exit, which confirms by using the acoustic technique.
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The Dielectric Properties in Frequency Domain of the 22 kV Underground Cables with Defective Joint
(2023-01-01)
Udomluksananon, Patt
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Jeenmuang, Siwakorn
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Chumpiboon, Komin
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Dorkmai, Kritsada
;
Rojanasunan, Warisanan
The failure that occurs in the underground cable systems leads to losses in many aspects, not only in the power system but also in the commercial and business. The most failure location in medium voltage underground cable systems is cable joint and cable termination, where the defects occur from poor workmanship. This paper represents the mean to investigate the dielectric properties of the 22 kV XLPE underground cable system to assess the insulation's integrity of the underground cable system. In the experiments, the underground cable system specimens were prepared by simulating the defects in cable joints, i.e., the iron powder on the XLPE surface and the incision on the XLPE surface; moreover, the underground cable system with the healthy condition joint was prepared to represent the new (or unused) underground cable system. To compare the dielectric properties in the frequency domain of the 22 kV underground cable systems with defective joints and the healthy condition joint, the frequency domain spectroscopy (FDS), the off-line non-destructive test, was performed in this research. From the test results, the dielectric dissipation factor shows a significantly different value in the case of iron powder when compared with the healthy condition joint. It reveals the loss peak on the curve at a frequency of 1 Hz. However, the case of incision on the XLPE surface is almost similar to the healthy condition case. The real part of the complex capacitance of all three cases has a constant value in the measured frequency ranges using the log-log scale. However, the imaginary part capacitance shows the distinct value of all three cases, of which the trends are the same as the dielectric dissipation factor curve.
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THE DIELECTRIC CHARACTERISTICS OF 22 KV XLPE UNDERGROUND CABLES WITH DEGRADED ARTIFICIAL JOINT
(2023-01-01)
Udomluksananon, Patt
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Boonsaner, Nutthaphan
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Wiangtong, Theerayod
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Jeenmuang, Siwakorn
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Chumpiboon, Komin
This paper represents the dielectric characteristics of the 22 kV underground cable test specimen. Two 3 m XLPE underground cables were connected with the heat-shrinkable joint that has been simulated with some artificial defects. The healthy heat-shrinkable terminations are at both ends of the cable test specimen. For this research, the underground cables with the healthy joint, the joint with a copper powder contaminant on the XLPE surface, and the joint with an incision on the XLPE surface were prepared to perform the experiment. To compare the dielectric characteristics of the underground cables with the healthy joint and degraded artificial joints, the polarization and depolarization currents (PDC) measurements and the very low frequency-tangent delta (VLF-TD) testing, according to IEEE standard 400.2-2013, were conducted. From the PDC measurements, the test results are not clearly different for the underground cables with the defective joint when compared to the healthy joint case, except for the electrical conductivity and insulation resistance that show the difference between them. The VLF tangent delta parameters and mean tangent delta comparison curve show differences in each case, which can contribute to assessing the condition of the underground cable systems.
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INVESTIGATION OF STATOR WINDING INSULATION CONDITION OF MV MOTORS BASED ON DIELECTRIC RESPONSE MEASUREMENT
(2023-01-01)
Pattanadech, Norasage
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Jeenmuang, Siwakorn
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Dorkmai, Kritsada
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Chumpiboon, Komin
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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.

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