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Dielectric Response Analysis Characteristic of Service-Aged XLPE Cables
(2024-01-01)
Thongkong, Patchara
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Promphanich, Wiboon
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Udomluksananon, Patt
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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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The Experiment of VLF Tanδ on Service-aged MV Underground Cable
(2024-01-01)
Tangthanam, Worasak
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Bunlaksananusorn, Chanin
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Suksawat, Dusit
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Udomluksananon, Patt
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Jeenmuang, Siwakorn
This paper presents the service-aged MV underground cable experiment using very low frequency (VLF) testing. The underground cables in this experiment have been utilized in service for more than 10 years and subjected to TEAM stresses, particularly with moisture, throughout the service time. So, the effect of moisture leads these cables to bad condition. The cables under the experiments are both service-aged and unaged. These cables were prepared the same by peeling both end sides of the cables and were terminated with high voltage insulating tape. The VLF test combined with the tangent delta (tanδ) measurement, according to IEEE Std. 400.2-2013 was performed to assess the condition of these cables and compare them with the unaged cable. The test results revealed that according to IEEE standard 400.2-2013, the service-aged underground cables were assessed in Action Required criteria. Still, the unaged underground cable was assessed in the Further Study Required criteria. Moreover, the tanδ values from service-aged underground cables have significant differences, with service-aged underground cables having higher values than unaged cables. Besides, the variation of tanδ data samples at each test voltage level from some underground cables shows a decreasing trend at 1.0U0 and 1.5U0. Nevertheless, the test voltage at 0.5U0 shows the constant trend of tanδ samples. This analyzed result can indicate that the insulation condition has humidity inside the cable insulation.
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Effect of Longtime Sheath Current on Insulation Screen of 115kV XLPE Underground Cable
(2024-01-01)
Jariyanurat, Kittipod
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Jeenmuang, Siwakorn
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Udomluksananon, Patt
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Kerdmanee, Sittipong
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Lacharochana, Sakda
Due to the need to extend the life of underground cables that are universally installed and used in power plants in Thailand, The life assessment must be concerned with advanced techniques, both chemical and physical, exactly. The components that needed to be analyzed were divided into two main groups: the insulation and physical systems. One of the most requisites is pyrolysis. Pyrolysis can occur in the underground cable system with many factors, for instance, the ambient temperature, overload, loss of connector, and longtime sheath current. Thus, this paper described the effect of the longtime sheath current on the insulation screen of 115kV XLPE underground power cable. Sheath current that ran into the system for longtime effectively effected to the insulation screen by destroying the structure of chemical properties leading to the short lifetime and getting the high risk to breakdown with the continue use.
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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
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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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Off-line and On-line Automatic and Unsupervised Partial Discharge Diagnostics of Electrical Asset Components
(2024-01-01)
Pattanadech, Norasage
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Jeenmuang, Siwakorn
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Udomluksananon, Patt
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Chumpiboon, Komin
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Shafiq, Muhammad
This paper deals with applications of an innovative approach to on-line and off-line partial discharge (PD)-based condition maintenance, where PD detection and analytics are fully automatic and do not require the support of PD experts. PD was measured off-line on a 50 kV A, 22/0.4 kV distribution transformer and on 115 and 230 kV transformer bushings, showing in both cases that PD can be detected and analyzed automatically according to the SID (Separation, Recognition, Identification) procedure. On-line measurements performed on MV generators are also reported and discussed, highlighting that there is potential for on-line MV (and HV) monitoring with automatic and unsupervised noise rejection, and identification of PD phenomena that can feed health assessment software to reach optimized maintenance plans.
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Physical and chemical properties’ comparison of natural ester and palm oil used in a distribution transformer
(2023-03-01)
Kittikhuntharadol, Yannaphol
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Pattanadech, Norasage
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Maneerot, Sakda
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Jongvilaikasem, Korraya
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Jariyanurat, Kittipod
Because of its low cost and suitable qualities, mineral oil (MO) has been commonly employed in transformers. Alternative liquid insulations with great characteristics have recently been presented. Natural ester (NE) and palm oil (PO) are considered alternative liquid insulations. This paper aims to study the physical and chemical properties of NE and PO which were used in a transformer for 21 months. All of the liquid insulation test specimens were sampled every 3 months. Physical properties of the liquid insulation, i.e., interfacial tension (IFT), viscosity, and particles count, were examined. Chemical properties of the liquid insulation, i.e., moisture content, acidity, corrosive sulfur, and furanic compound (2-FAL), were investigated. IFT, particles count, moisture content, acidity, and 2-FAL test results indicated deterioration of liquid insulations of the used liquid insulation; however, there is no observation change for particles amount and acidity of NE. The other test results were not found significantly change.
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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
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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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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.
1
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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.
1
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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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