KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 12

Some of the metrics are blocked by your
consent settings
Dielectric analysis of degraded stator bars of a hydro generator
(2022-04-01)
Pattanadech, Norasage
;
Phumipunepon, Natnaree
;
Srinangyam, Chissanupong
;
Jeenmuang, Siwakorn
;
Bunlaksananusorn, Chanin
This paper presents the investigation of dielectric analysis of degraded stator bars by Polarization and Depolarization Current (PDC) measurement. The stator bars obtained from the 30-year in-service synchronous machine were divided into two groups. The first group was the unmodified stator bars. The second group was the simulated degradation stator bars which were composed of the thermal stress stator bars, conductive tap abrasion stator bars, multiple air cavity stator bars, multiple oil filled stator bars and multiple water filled stator bars. PDC test experiment was performed with the stator bar samples. PDC test results were analyzed in time domain and in frequency domain with the derived parameters i.e. R<inf>dc</inf>, real and imaginary part of complex capacitance, C ratio, conduction loss factor and polarization loss factor. It was found that PDC shapes obtained from the conductive tape abrasion stator bar and multiple water filled cavity stator bar were clearly different from that of the unmodified stator bar. For other case studies, the derived parameters showed the usefulness in analysis the degraded stator bar characteristics. For example, the increase in the imaginary capacitance and conduction loss factor can be observed from most cases of degraded stator bar test results.
Some of the metrics are blocked by your
consent settings
The Study of Polarization and Depolarization Current Measurements on Service-Aged 22 kV XLPE Underground Cables with Presence of Water Trees
(2022-01-01)
Udomluksananon, P.
;
Kunakorn, A.
;
Maneerot, S.
;
Bunlaksananusorn, C.
;
Pannil, P.
This paper represents the condition assessment of service-aged 22 kV XLPE insulated underground cables. From the investigation, the water trees were detected in the insulation layer. The visual inspection of underground cables reveals the presence of copper carbonate contaminated on the copper tape layer. Some underground cables have the discontinuity of the copper tape layer. To evaluate the insulation condition of the underground cables, the polarization and depolarization current (PDC) measurements were performed on both the service-aged and the new (or unused) cables. The underground cables to experiment with the length of insulation screen equal to 1 m were prepared. In this research, the PDC measurements were performed on different aspects, i.e., the testing voltages (600 V, 800 V, and 1000 V), the testing positions, the effect of the discontinuity of the copper tape layer which occurred during service, the influence of the presence of copper carbonate, and the influence of water trees in XLPE cables. The dielectric response of the underground cables by using polarization and depolarization current measurements can diagnose the problems in service-aged underground cables, but this paper needs more test data for accurate interpretation.
Some of the metrics are blocked by your
consent settings
VLF dielectric response and HF localized dielectric discharge measurement for rotating machine insulation assessment
(2020-08-14)
Nimsanong, P.
;
Pattanadech, N.
This paper represents the very low frequency (VLF) dielectric response and high frequency (HF) localized dielectric discharge measurement for rotating machine insulation assessment. The integral conditions of stator winding insulation, the so-called aging condition, were investigated by the dielectric response measuring technique. The polarization and depolarization currents in the VLF range from 0.0001 to 1 Hz were measured under an external step electric field. The local conditions of stator winding insulation, the so-called weak spot condition, were examined by the partial discharge (PD) measuring technique. The PD pulse currents were detected by a capacitive sensor in a wide-band range, where the bandwidth of the measuring system was set between 30 kHz and 30 MHz. The medium voltage rotating machine rated 6.6 kV and 240 to 2,270 kW under different service conditions, i.e., new stator winding, moisture contamination, dirt contamination as well as thermally and severely aged insulation, was studied. Besides, four case studies on measuring the PD in service rotating machines rated 11–15 kV, 7100 to 211,000 kW as well as the attenuation of the PD pulses were conducted and demonstrated. With several case studies, this paper introduces new dielectric parameters, the so-called charge ratio (QR) and charge difference gradient (QDG), to identify the dielectric mechanism occurring in the stator winding insulation caused by the polarization and conduction processes. It can be concluded that the proposed parameters are a valuable tool for assessing the aging condition. In the case of the PD measurement, it was found that the PD pulse is strongly attenuated in the slot section. This paper also introduces the combination of both the dielectric response and PD measurement results, which can be very useful for assessing a complete insulation condition in the rotating machine. Moreover, the criteria for insulation conditions are suggested in this paper to evaluate the integral and local conditions for the rotating machine insulation. The local discharge in the machine causes electromagnetic waves, which may get released from the non-perfect characteristics of the enclosure. This signal may interfere with the functioning of other nearby electronic devices, especially the communication equipment. Therefore, maintaining the excellent condition of the insulation system by the proposed technique detailed in this paper will support the highly effective operational efficiency of the communication system as well.
Some of the metrics are blocked by your
consent settings
Dielectric response analysis for cable joint problems in medium voltage underground cable system
(2020-01-01)
Klienhom, Sitthisak
;
Boonsaner, Nutthaphan
;
Nimsanong, Phethai
;
Chancharoensook, Phop
;
Kunakorn, Anantawat
This paper represents the investigation of dielectric response analysis of a cable system composed of a medium voltage XLPE underground cable, a heat-shrink cable joint and a heat-shrink cable termination. A 12/20(24) kV single core XLPE underground cable with the nominal cross-section area of 240 mm2, three pieces of 22 kV cable joints, and eight pieces of 22 kV cable termination were prepared for the experiment. Then, polarization and depolarization current (PDCs) measurement were performed. The experiments were divided into two parts. The first part was composed series of three tests, A — C, and the second part consisted series of two tests, D — E, as follows: Test A examined dielectric response of a 6 m healthy XLPE underground cable, Test B examined dielectric response of a 6 m healthy XLPE underground cable with two healthy cable terminations, Test C examined dielectric response of a two of 3 m healthy XLPE underground cable with healthy cable terminations connected by a healthy cable joint, Test D used the test object similarly as case C but the cable joint was contaminated with copper particles, and Test E used the test object similarly as case C but the cable joint was contaminated with tiny pieces of water blocking. From the experiment, the PDCs and the derived dielectric parameters such as geometrical capacitance, insulation resistance, polarization index, depolarization index, charge difference curve and charge ratio curve were analyzed. The PDCs and the derived parameters were found different for each case of study as details in this paper. Besides, the charge ratio proposed by authors is a valuable parameter for the diagnosis of insulation system of high voltage equipment.
Some of the metrics are blocked by your
consent settings
Polarization and Depolarization Current Measurement for Foreign Object Detection in Gas-Insulated Transmission Line
(2019-10-01)
Nganpitak, Tritod
;
Chancharoensook, Phop
;
Pattanadech, Norasage
Polarization and depolarization current (PDC) test is one of non-destructive insulation test method that usually uses for diagnosis the solid and liquid insulation problems. In case of gas-insulated transmission line (GIL), it not only comprises of gas insulation but also the solid insulation such as cone insulators. This paper presents the PDC measurement for foreign object detection in GIL. A 230kV, 2500A, single phase GIL with 2 m length was used in the PDC experiments. The external diameter of this GIL conductor and enclosure are 92 and 366 mm respectively. In the experiment, defects on the cone insulator was simulated in three cases, i.e. 1) cone insulator was attached with a paper tape, 2) cone insulator was attached with an aluminum foil, 3) cone insulator was attached with a moist paper. The width of the simulation defect was approximately 2 mm. The lengths of the simulation defects were varied from 25 - 200 mm depending on defect types. PDC test results obtained from the GIL with the simulated defect cone insulators were compared with that of clean and dry cone insulator as reference. The results of the experiments showed that PDC curves obtained from GIL with the simulated defect cone insulators were clearly different from that of the reference case. Other analyses are reported in the paper.
Some of the metrics are blocked by your
consent settings
Polarization and depolarization current measurement applied for investigation of underground cable system problems
(2019-07-01)
Pattanadech, N.
;
Phongsirichairojna, T.
;
Navapittayaratana, N.
;
Nimsanong, P.
;
Jirathipchaisakul, T.
This research investigates the problems in XLPE cables system. The 12/20(24) kV underground cable with the cross section area of 240 mm2 was used in the experiment. Two 3 meter long cables were connected by a cable joint where the defect was simulated on. The dielectric investigation of XLPE cable system by polarization and depolarization current (PDC) measurement was performed comparatively among four different cases: a healthy cable with healthy heat shrinkable joint (case1), a cable joint with an incision on XLPE surface (case2), a cable joint contaminated with 20 micron iron powder on XLPE surface (case3) and a cable joint contaminated with 20 micron copper powder on XLPE surface (case4). Diagnostic parameters, PDC shapes, dielectric dissipation factor (DDF) and conduction current, derived from PDC test results for analyzing the dielectric response are proposed in this paper.
Some of the metrics are blocked by your
consent settings
Dielectric properties of stator coil insulation of medium voltage motor
(2019-07-01)
Pattanadech, N.
;
Boonsathitthavorn, S.
;
Phumipunepon, N.
One of the non-destructive methods commonly used to characterize the electrical properties of power devices is polarization and depolarization current (PDC) method. The objective of this paper is first to compare the dielectric properties of the stator coil without overhang insulation, the stator coil after hot-press process, and the stator coil with overhang insulation. The second objective is to compare dielectric properties of newly wound stator coil, the stator coil heated at {\mathrm {60^{\circ}C}}, and the stator coil heated at {\mathrm {90^{\circ}C}} for a specific time. The stator coils in this research were designed for a 6.6 kV 260 kW synchronous motor. For the stator coil without overhang insulation, the slot portion stator coil was wound by Nomex paper, Kremica tape, and conductive tape. For the overhang insulation, the end portion was wound by Filosam tape and polyester tape. Then, the PDC measurement was performed. The parameters from PDC analysis were used to assess dielectric properties. These parameters were composed of the PDC shapes, capacitance ratio, polarization loss and conduction loss. Test results showed that different insulation types applied for each part of the stator coil manufacturing provided different dielectric properties. This point should be considered when PDC measurement is performed with the whole insultion system of the high voltage motors.
Some of the metrics are blocked by your
consent settings
Polarization and depolarization current characteristics of thermally stressed stator bars
(2019-07-01)
Pattanadech, N.
;
Srichuen, N.
;
Wang, C.
;
Kaewdee, N.
;
Poungpat, T.
Polarization and depolarization current (PDC) measurement was used in this research to investigate the insulation integrity of stator bars. This method is non-destructive testing. This paper presents the PDC analysis of thermally stressed stator bars divided into two main groups. The first group was heated at 100^{\circ}C and the second group was heated at 130 ^{\circ}C for 36 hours. After 12, 24 and 36 hours of heating process, PDC measurement of each test specimen was performed. PDC test results including capacitance ratio and dielectric dissipation factor were analyzed and reported.
Some of the metrics are blocked by your
consent settings
The investigation of insulation performance evaluation of the large electrical rotating machine in frequency domain
(2019-01-01)
Phloymuk, Natthawut
;
Kando, Masaaki
;
Pattanadech, Norasage
The insulation structure of winding in a large electrical rotating machine consists of epoxy resin and mica material. The insulation structure is composed of many junctions. The insulation problems generate different kinds of signals, such as electromagnetic waves, which may get released from the non-perfect characteristics of the enclosure. This signal may interfere with the functioning of other nearby electronic devices. Therefore, maintaining an excellent condition of the insulation system of the machine is very important. For a condition monitoring of this insulation as proposed in this research, it is taken into consideration the results of the polarization and depolarization current (PDC) measurement of the test sample, and the stator winding rated 13.8 kV was investigated. The experiments were conducted under different thermal stresses, i.e., 25◦C (the room temperature) and 100◦C (the operation temperature). The test samples were divided into three types: I. haft-overhang, II. overhang and III. full stator bar. From the PDC measurement data record, the complex capacitance and polarization losses (ion migration polarization, slow relaxation polarization and interfacial polarization) were calculated. It was found that the aging of the insulation related to the complex capacitance and polarization losses can be contributed for research in future wireless technology.
Some of the metrics are blocked by your
consent settings
The classification of regular and defected low voltage XLPE cable by using polarization and depolarization current method
(2017-10-19)
Singhasivanon, J.
;
Manop, C.
;
Pattanadech, N.
;
Jirasuwankul, N.
Electric cable is an important part of utility power and distribution system. In order to keep the system operation safely and reliable, acceptance testing for cable is necessary not only inservice but also manufacturing process. This paper proposes a novel testing technique which is able to classify the difference between normal and defective low voltage XLPE cable, namely polarization and depolarization current technique (PDC). In this study, PDC testing of low voltage XLPE cable was performed comparatively among five different cases: cable contaminated with a piece of paper, case 2 : cable contaminated with a piece of plastic, case 3 : cable contaminated with grease, case 4 : cable contaminated with a piece of copper, and case 5 : Eccentric conductor cable. With environmental control of the testing process, the test results show the polarization current of the defective contaminated cable with copper is higher than that of the regular one, whereas it is lower than that of the defective one with paper, plastic and grease. It is also found that there was indistinctive of PDC in case of copper contaminated and eccentric conductor cable.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results