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Author: search.filters.author.Pattanadech, N.Subject: search.filters.subject.Polarization and depolarization current

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    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.
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    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.
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    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 mm<sup>2</sup> 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.
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    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.
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    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.
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    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.
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    Dielectric diagnosis of 24kV XLPE cable using polarization and depolarization current, conventional partial discharge measurements and high frequency current measurement
    (2016-01-01)
    Nimsanong, P.
    ;
    Pattanadech, N.
    ;
    Yutthagowith, P.
    Medium voltage power cables are an important element of electric power distribution. Most of cable failures occurring in XLPE insulation and cable accessories are due to insulation failure. This research work represents the dielectric investigation of 12/20(24) kV XLPE power cables including cable joints by using polarization and depolarization current (PDC) measurement, conventional partial discharge measurement according to IEC 60270, and high frequency current measurement measured by high frequency current transformer (HFCT). In this research work, six case studies, case 1: PE sheath damaged, case 2: semi-conducting layer damaged, case 3: void defect in extruded cable, case 4: void defect in extruded cable at cable joint, case 5: semiconductive contaminant at cable joint, and case 6: conductive contaminant at cable joint, were investigated. The test results showed that two basic properties, polarization and depolarization current, of cable insulation can be utilized for classification of cables with joint problems. The defects in extruded cable and cable joint can be identified by the PDC shapes. However, to clarify the problems occurring at the cables by conventional PD measurement and HFCT measurement was performed. Moreover, it was found that the sensitivity of HFCT was clearly lower than conventional tool.
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    Equivalent circuit approximation of transformer insulation by using PDC measurement
    (2008-10-06)
    Roongroj, Ch
    ;
    Pattanadech, N.
    ;
    Praisuwanna, P.
    ;
    Yutthagowith, P.
    ;
    Thongkaemkaew, K.
    This paper represents the insulation model of 3φ, 50 MVA, 132.8/13.8 kV power transformer. This model is developed from the polarization and depolarization current measurement (PDC). The insulation modeling consists of a parallel circuit among C<inf>50</inf> <inf>Hz</inf>, R<inf>0</inf>, R <inf>1</inf> and C<inf>1</inf> in series, R<inf>2</inf> and C<inf>2</inf> in series, R<inf>3</inf> and C<inf>3</inf> in series, and R<inf>4</inf> and C <inf>4</inf> in series. C<inf>50</inf> <inf>Hz</inf> is obtained from the conventional measurement method; whereas, the applied step voltage and the sum of PDC are calculated for R<inf>0</inf>. The individual elements (R<inf>1</inf> and C<inf>1</inf>) are determined from fitting technique employing MATLAB program. From experimental results of the tested transformer, the example of insulation model for Transformer No. 1 (T1) is created with C<inf>50</inf> <inf>Hz</inf> of 3.643 nF, R<inf>0</inf> of 334.8 GΩ. The values of R <inf>1</inf>-R<inf>4</inf> are 86.52, 110.5, 669.5 and 271.0 GΩ respectively; while, the values of C<inf>1</inf>-C<inf>4</inf> are 37.62, 6.047, 0.101 and 0.013 nF respectively. The proposed model is validated by calculating dissipation factor and measuring dissipation factor. The results show that the proposed model and experimental validation are good agreement with each others. © 2008 IEEE.