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Omicron CP TD1 Reference Manual

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Summary of Contents for Omicron CP TD1

  • Page 1 CP TD1 Reference Manual...
  • Page 2 All rights including translation reserved. Reproduction of any kind, for example, photocopying, microfilming, optical character recognition and/or storage in electronic data processing systems, requires the explicit consent of OMICRON electronics. Reprinting, wholly or in part, is not permitted. The product information, specifications, and technical data embodied in this manual represent the technical status at the time of writing and are subject to change without prior notice.

  • Page 3: Table Of Contents

    CP TD1 Connected to a Test Object ....... . .
  • Page 4 CP TD1 Reference Manual V 1.44 Measurement of Capacitance and Dissipation Factor / Power Factor..54 "UST" and "GST" Measurements Using the Guard Technology ... . 58 References .
  • Page 5 Technical Data ..........119 11.1 Technical Data of the CP TD1 in Combination with the CPC 100 ..119 11.1.1 High-Voltage Output .
  • Page 6 OMICRON Service Centers ........185...

  • Page 7: Using This Manual

    The CP TD1 Reference Manual always has to be available on the site where the CP TD1 is used. It must be read and observed by all users of the CP TD1. Reading the CP TD1 Reference Manual alone does not release you from the duty of complying with all national and international safety regulations relevant to working on power transformers.
  • Page 8 CP TD1 Reference Manual V 1.44 Symbols Used In this manual, the following symbols indicate paragraphs with special safety relevant meaning: Symbol Description Caution: Equipment damage or loss of data possible Warning: Personal injury or death of the operating staff or...

  • Page 9: Safety Rules

    Preface Safety Rules Before operating the CP TD1, read the following safety rules carefully. If you do not understand some safety rules, contact OMICRON electronics before proceeding. Maintenance and repair of the CP TD1 is only permitted by qualified experts at OMICRON electronics repair centers.
  • Page 10 CP TD1 Reference Manual V 1.44 Safe area High-voltage area Figure 1-1 Example for the separation of safe and high-voltage area using different OMICRON electronics devices...
  • Page 11 • The high-voltage cable must always be well attached and tightly connected to both the CP TD1 and the test object. A loose or even falling off connector at the test object carrying high-voltage is life-hazardous. Make sure the connectors are clean and dry before connecting.
  • Page 12 Orderly Measures The CP TD1 Reference Manual or alternatively the e-book in PDF format has always to be available on site where the CP TD1 is being used. It must be read and observed by all users of the CP TD1.
  • Page 13 Preface Disclaimer If the equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment may be impaired. Static Charges Static charges on bushings or other apparatus such as transformer windings may be induced by test potentials. While the voltage may not be significant enough to do any damage, it can be a source for serious accidents due to falls caused by reflex action.
  • Page 14 CP TD1 Reference Manual V 1.44...

  • Page 15: Introduction

    • Test voltage & current The CP TD1 works as an add-on device to the CPC 100. Do not connect the CP TD1 to any other device. Do not use the accessories for applications not indicated in this user manual.

  • Page 16: Functional Components Of The Cpc 100 And Cp Td1

    CP TD1 Reference Manual V 1.44 Functional Components of the CPC 100 and CP TD1 Equipment trolley Cable drum with double-shielded output cable to feed the high voltage to the test object. CPC 100 Cable drum for measuring cables Booster cable ⇔...
  • Page 17 (short type). Via this data cable, the CPC 100 software (test card TanDelta) controls the CP TD1. CP TD1’s measuring inputs IN A and IN B, connected to the cable drum for the measuring cables. Swivelling mounting brackets for the CPC 100 (top)

  • Page 18: Functional Components Of The Cp Td1

    Functional Components of the CP TD1 1.3.1 Grounding Terminal and Booster Input Grounding Booster Input terminal Figure 1-2 Grounding terminal and booster input of the CP TD1 1.3.2 Serial Interface Connector and Measuring Inputs Serial interface connector IN_A IN_B measuring...

  • Page 19: High-Voltage Connector

    Introduction 1.3.3 High-Voltage Connector Grounding terminal High- voltage connector Figure 1-4 High-voltage connector of the CP TD1...
  • Page 20 CP TD1 Reference Manual V 1.44...

  • Page 21: Operation

    2.1.2 Setup of Devices without Trolley If the CPC 100 and CP TD1 are to be operated without trolley, place them on their transport cases and connect them with the long type data cable CPC 100 ⇔ CP TD1 (3m) and the long-type booster cable CPC 100 ⇔ CP TD1 (3m).

  • Page 22: Cp Td1 Connected To A Test Object

    CP TD1 Reference Manual V 1.44 CP TD1 Connected to a Test Object HV area CP TD1 12 kV IN A IN B Measurement Booster Serial CPC 100 Power transformer Safe area Grounding terminal...

  • Page 23: Cp Td1 Connected To Cp Cal1

    50 ... 200Hz. Calibrating the CP TD1 Using a Reference Capacitor Warning: For using the CP CAL1, make sure to apply the same procedure as described in this Reference Manual.

  • Page 24: Calibration Tips

    DF/PF + = DFref - DFmeas as described in 3.3 on page 29. A re-calibration of the CP TD1 is also shown in the test report (.xml file). Note: If you change the factory-made calibration, the responsibility for the accuracy of the CP TD1 will be in your hands.

  • Page 25: Test Cards

    "Auto test points" cleared = manual measurement: Applies the set test voltage and frequency to the CP TD1’s output. When the measurement is finished, its results are displayed in the results table.
  • Page 26 2000V and 2001V. The CP TD1 then puts out the specified list of values as follows: 1. All voltages are issued in the exact order they were entered using the first frequency value of the list.
  • Page 27 Test Cards Measuring modes and their according arrangements of the internal switch-matrix in the CP TD1 The switch-matrix determines what capacities are actually measured.

  • Page 28: Tandelta Test Card - Main Page (2/2)

    Ls, Q = series inductance & quality factor The averaging factor determines the number of measurements. A factor of 3 means: the CP TD1 carries out 3 measurements whose results are then averaged. The higher the factor, the more accurate the measurement but the longer the measuring time.

  • Page 29: Tandelta Test Card - Settings Page (1/2)

    If this is the case, it makes sense to clear the check box. Warning: Never operate the CP TD1 with unconnected shield of the high- voltage cable. If the "Perform shield check" check box is cleared, make sure...

  • Page 30: Tandelta Test Card - Settings Page (2/2)

    CP TD1 Reference Manual V 1.44 TanDelta Test Card - Settings Page (2/2) Selecting "Compensations" converts the actually measured dissipation or power factor to normalized values corresponding to an ambient temperature of 20°C. In doing so, the values entered at "Compensations" represent the existing ambient condition.

  • Page 31: Templates

    Test Cards Templates The test procedures for designated applications are controlled by templates available on the CPC Toolsets shipped with your CP TD1 or on the CPC 100 Start Page. The templates are pairs of XML documents and Microsoft Excel templates designed by OMICRON electronics for designated applications.
  • Page 32 CP TD1 Reference Manual V 1.44...

  • Page 33: Application

    • If there is a longer distance between the location of the CP TD1 and the area of danger (that is, the test object), a second person with an additional "Emergency Stop"...
  • Page 34 6. Pull out the measuring cables from the cable drum and connect the test object to the CP TD1’s measuring inputs IN A and IN B. 7. Connect the high-voltage cable from the test object to the CP TD1’s high- voltage output.

  • Page 35: Measurement

    CPC 100 Reference Manual. 2. Selecting the TanDelta - PF test card from the CPC 100’s menu automatically turns on the CP TD1. If no CP TD1 is connected to the CPC 100, an error message occurs.

  • Page 36: Disconnection

    4. Once all test cards are prepared and the parameters set, make sure the safety key lock is in position "release" (horizontal). Warning: If you have a cardiac pacemaker, do not use the CP TD1! Before operating the CP TD1, make sure there is no person with a cardiac pacemaker in the immediate vicinity.
  • Page 37 Warning: Earth-connect and shorten out the test object’s terminals using a grounding set. 4. Plug off the high-voltage cable from the high-voltage output of the CP TD1. 5. Disconnect the cables from the CP TD1.
  • Page 38 CP TD1 Reference Manual V 1.44...

  • Page 39: Capacitance And Dissipation Factor Measurement

    Capacitance and Dissipation Factor Measurement Capacitance and Dissipation Factor Measurement Capacitance (C) and Dissipation Factor (DF) measurement is an established and important insulation diagnosis method. It can detect: • Insulation failures • Aging of insulation • Contamination of insulation liquids with particles •...
  • Page 40 CP TD1 Reference Manual V 1.44 capacitance and R the losses (Figure 5-1). Losses can also be represented by serial equivalent circuit diagram with C and R (chapter 12.1). The definition of the dissipation factor and the vector diagram are shown in Figure 5-2.
  • Page 41 Capacitance and Dissipation Factor Measurement δ ----------------- - ω C δ δ Figure 5-2 Definition of dissipation factor (tan ) and the vector diagram...
  • Page 42 CP TD1 Reference Manual V 1.44 ϕ The correlation between the Dissipation Factor and Power Factor (PF = cos and the vector diagram are shown in Figure 5-3. Withδ 1 « δ ≅ δ ≅ ϕ π δ -- - ϕ...
  • Page 43 Capacitance and Dissipation Factor Measurement The dielectric losses in the insulation are caused by: • movement of conductive particles • movement of ions and electrons • polarization effects (Figure 5-4) Kind of polarization Suspension Rotation Electrons Ions Dipoles completely reversible partly reversible partly irreversible All Material...
  • Page 44 CP TD1 Reference Manual V 1.44 Polarization losses are generated due to suspension and rotation effects. Suspension of electrons is completely reversible. Figure 5-5 shows this mechanism. This kind of polarization is also called "Atom Polarization". core Way of electrons...
  • Page 45 Capacitance and Dissipation Factor Measurement without E with E Figure 5-7 Polarization of dipoles in the electrical field...
  • Page 46 CP TD1 Reference Manual V 1.44 A typical dipole is a water molecule. Figure 5-8 shows such a molecule in the electrical field. When the electrical field changes the polarity, the orientation of the water molecule is changed by 180°. This rotation, along with the applied frequency, causes the described losses.
  • Page 47 Capacitance and Dissipation Factor Measurement charge region. These space charge regions are moved back and forth through the field. This effect, for example, occurs on the interface between transformer oil and solid insulation like paper or transformer board (Figure 5-9). ε...
  • Page 48 CP TD1 Reference Manual V 1.44 Influence of different parameters like water content, temperature and aging on DF Figure 5-10 shows the breakdown voltage and the DF in oil, dependent on the water content [2.3]. With low water content, the breakdown voltage is very sensitive;...
  • Page 49 Capacitance and Dissipation Factor Measurement Figure 5-11 shows the DF of new and used oil, dependent on the temperature. With higher temperatures, the viscosity of the oil decreases so the particles, ions and electrons can move easier and faster. Thus the DF increases with temperature [2.3].
  • Page 50 CP TD1 Reference Manual V 1.44 Figure 5-12 and table 5-1 show a temperature correction factor (according to ANSI 57.12.90) for insulation based on mineral oil [2.4]. Figure 5-12 Temperature correction factor for mineral oil insulation [2.4] ------ - where is the power factor corrected to 20°C...
  • Page 51 Capacitance and Dissipation Factor Measurement Table 5-1 Temperature correction factor for mineral oil insulation [2.4] Test temperature T (°C) Correction Factor K 2.18 2.42 2.70 3.00 Note: The correction factors listed above base on insulated systems using mineral oil as an insulating liquid. Other insulating liquids may have different correction factors.
  • Page 52 Temperature behavior RBP, RIP, and OIP bushing [2.5] The dissipation factor is dependent on the frequency. With modern test devices like the CPC 100 + CP TD1, it is possible to cover a wide frequency range for capacitance and DF measurements. Up to now, fingerprint measurements for comparison are normally available only at line frequency.
  • Page 53 Capacitance and Dissipation Factor Measurement TR 2-Winding DF (f) 0.55% 0.50% L (f) 0.45% HL (f) 0.40% H (f) 0.35% 0.30% 0.25% 0.0Hz 100Hz 200Hz 300Hz 400Hz 500Hz Figure 5-15 Frequency scan winding to winding DF measurement (oil- paper) DF (f) 0.67% 0.66% 0.65%...

  • Page 54: Measurement Of Capacitance And Dissipation Factor / Power Factor

    CP TD1 Reference Manual V 1.44 The dissipation factor is in many cases also dependent on the test voltage. Figure 5-17 shows a measurement of a 6kV motor. Above 4kV, partial discharges occur. This is the reason for the rise of DF.
  • Page 55 Capacitance and Dissipation Factor Measurement free reference capacitor. The parallel circuit diagram shown in Figure 5-1 can be transferred as a direct equivalent into this serial diagram at specified frequencies (section 12.1). ------------ - ----- - jωC jωC ------------------------- ------------------------- jωC Figure 5-18 Schering bridge...
  • Page 56 Figure 5-19 CP TD1 measuring principle The CP TD1 test system utilizes a method similar to that of the Schering bridge. The main difference is that the CP TD1 measuring principle (Figure 5-19) does not require tuning for measuring C and DF. C is a gas insulated reference capacitor with losses below 10E-5.
  • Page 57 Capacitance and Dissipation Factor Measurement The CP TD1 takes all these effects into account and compensates for them electronically, so it is now possible for the first time to measure in the field down to DF = 5 x 10E-5. Figure 5-20 shows the complete equivalent circuit diagram.

  • Page 58: Ust" And "Gst" Measurements Using The Guard Technology

    CP TD1 Reference Manual V 1.44 "UST" and "GST" Measurements Using the Guard Technology In electrical devices like power transformers there are a lot of insulation gaps, which have to be checked separately: • Winding to winding • Winding to tank & core •...
  • Page 59 For the separate measurement of all capacitors a so-called guard technique is necessary. The single capacitors connected to guard are energized but not measured. In Figure 5-22 a block diagram of the CP TD1 is shown with the guard connection and measuring input. In the example case C and C capacitors, connected to the CP TD1.
  • Page 60 In the GST mode all connected capacitors are measured in parallel (C HL + C HT + C H). This way we can check if the CP TD1 is overloaded during the measurements or not (Figure 5-23) and we can check the single measurements.
  • Page 61 Capacitance and Dissipation Factor Measurement Now we want to measure C HL. The connection diagram is shown in Figure 5-24. The measuring mode is UST-A. IN A IN B UST-A C = C Figure 5-24 Measurement of C HL in UST-A mode, C HT and C H are guarded...
  • Page 62 CP TD1 Reference Manual V 1.44 Next measurement is C HT. The connection diagram is shown in Figure 5-25. The measuring mode is UST B. Without the GUARD technique it would not be possible to measure C HT separately, because C HL in series to C LT are in parallel to C HT.

  • Page 63: References

    Capacitance and Dissipation Factor Measurement The last measurement is C H. Figure 5-26 shows this connection diagram. The measuring mode is GSTg-A+B. C HL and C HT are not measured, because they are connected to GUARD. The build-in relay matrix enables the described four different measurements without any rewiring.
  • Page 64 CP TD1 Reference Manual V 1.44 [2.5] Seitz, V.: "Vorbeugende Instandhaltung an Leistungstransformatoren – Betriebsbegleitende Messungen an Stufenschaltern und Durchführungen, OMICRON Anwendertagung 2003, Friedrichshafen...

  • Page 65: Power Transformers

    Power Transformers Power Transformers Introduction Due to ever-increasing pressure to reduce costs, the power industry is forced to keep old power facilities in operation as long as possible. In most European countries, about one third of the transformers are over 30 years old. Even transformers older than 50 years are still in service.
  • Page 66 CP TD1 Reference Manual V 1.44 Legend: Major gases Minor gases ppm = parts per million by volume (gas/liquid) Previous limits for CO were 500 and 700 ppm Previous limits for CO were 2000 and 10000 ppm Behind the absolute value of gas content are the quotients of the gas components, which also allow for additional information (Table 6-1) [3.2].
  • Page 67 Power Transformers Possible Faults and Possible Findings Table 6-2 Possible Faults and Possible Findings [3.3] Key gases Possible Faults Possible Findings , possible trace of Partial discharges Weakened insulation (corona) from aging and electrical and C stress Possible CO. , CH (some CO if Low energy discharges Pinhole punctures in...
  • Page 68 CP TD1 Reference Manual V 1.44 Transformer Faults Table 6-3 Transformer Faults [3.3] Fault Examples Partial discharges Discharges in gas-filled cavities in insulation, resulting from incomplete impregnation, high moisture in paper, gas in oil supersaturation or cavitation (gas bubbles in oil), leading to X wax formation on paper.
  • Page 69 Power Transformers Table 6-3 Transformer Faults [3.3] Fault Examples Overheating 300°C - 700°C Defective contacts at bolted connections (especially busbar), contacts with tap changer, connections between cable and draw-rod of bushings. Circulating currents between yoke clamps and bolts, clamps and laminations, in ground wiring, bad welds or clamps in magnetic shields.

  • Page 70: Capacitance And Df Measurement Of Transformer Windings

    Measurement of leakage reactance • Capacitance and Dissipation factor measurement All the mentioned tests can be done with the CPC 100 + CP TD1. This instrument is the ideal test and analysis instrument for transformer diagnosis with these measuring possibilities.
  • Page 71 If the transformer has a tap changer then it should be set to the neutral position (0 or middle tap). • Connect the CPC 100 + CP TD1 ground terminal to the transformer's (substation) ground. • Connect the high-voltage output of the CP TD1, e.g. to the high-voltage...

  • Page 72: Three-Winding Transformer

    CP TD1 Reference Manual V 1.44 like the bushings and the transformer tank (flashovers) with the unscreened part of the high-voltage test cable must be avoided. • Connect the IN A, e.g. to the low-voltage winding, IN B, e.g. to the tertiary winding (according to the connection instructions).
  • Page 73 Power Transformers A three-winding transformer is much more complicated so more tests are necessary to measure all gaps. In Figure 6-2, a complete 3-winding power transformer is shown. The tertiary winding is not accessible in this case. When the load is unbalanced, it is necessary for flux compensation in the three limbs of the core.
  • Page 74 CP TD1 Reference Manual V 1.44 Phase A Phase B Phase C High-Voltage Cap. H to Ground C H-L Cap. H to winding Low-Voltage winding C L Cap. L to Ground C L-T Cap. L to T Tertiary winding Cap. T to Ground C H-T Cap.
  • Page 75 Power Transformers Tertiary winding Cap. T to Ground C H-T Cap. H to To check the winding insulation completely, it is necessary to measure the capacitance and the DF of all insulation gaps (in this case six capacitors). Caution: All phases and the neutral terminal of one winding (H, L and T) have to be short-circuited.
  • Page 76 CP TD1 Reference Manual V 1.44 HIGH TERT. – HIGH – TERT. TERT. – HIGH A more detailed test procedure for two- and three- winding transformers can be found in [3.6]. This test procedure is included in the appendix and is now used...
  • Page 77 CPC Editor. Due to the high amount of measuring data, the test is split into three single test files. The first file contains the tests with high-voltage winding connected to the CP TD1 high-voltage output: Figure 6-5 Input of transformer data...
  • Page 78 CP TD1 Reference Manual V 1.44 Figure 6-7 Measurement of C H and C H-L in GST g-B mode Figure 6-8 Voltage-scan of high-voltage windings to tank and core (GST gA+B)
  • Page 79 Power Transformers Figure 6-9 Frequency-scan of high-voltage windings to tank and core (GST gA+B) The other tests for H-L are prepared analog to the examples.
  • Page 80 CP TD1 Reference Manual V 1.44 A second test file contains the tests with the low-voltage winding connected to the high-voltage output of the CP TD1. Figure 6-10 shows the first screen with the connection instructions. Figure 6-10 Connection instructions for the tests with energized low-voltage...
  • Page 81 Power Transformers A third test file is used for the tests with the tertiary winding connected to the CP TD1 high-voltage output. 6-11 shows the connection instructions for the tests with energized tertiary winding. Figure 6-11 Connection instructions for the tests with energized tertiary...
  • Page 82 The prepared tests are uploaded to the CPC 100 as xml files without results. After the test is done, this xml file with the results is downloaded to the computer and loaded into Microsoft Excel with the OMICRON CPC 100 File Loader (the complete test files are included on the CD-ROM).
  • Page 83 Power Transformers Voltage and frequency scans enable additional information about the insulation quality. They should be saved as "fingerprint" for future measurements. For all the described measurements only three different connections of the test leads are necessary. Preparing the test in the office by utilizing the CPC Editor, the testing time on-site can be reduced to a minimum.
  • Page 84 CP TD1 Reference Manual V 1.44 Figure 6-14 Frequency scan for H-L (f) (5 kV)

  • Page 85: Two-Winding Transformer

    Power Transformers 6.2.2 Two-Winding Transformer The test of two-winding transformers is easier than the described test procedure for transformers with three windings. Figure 6-15 shows the simplified circuit diagram of a two-winding transformer. Core Tank Figure 6-15 Two-winding transformer with winding capacitances High-Voltage Cap.
  • Page 86 CP TD1 Reference Manual V 1.44 In Figure 6-16, the test procedure for a two-winding transformer is shown, according to IEEE 62 1995 [3.4]. HIGH Figure 6-16 Two-winding transformer test according to IEEE 62-1995 Test Mode Energize Ground Guard Measure HIGH –...

  • Page 87: Auto-Transformer

    Power Transformers Figures 6-17 and 6-18 show the preparation with the CPC Editor and the test results in MS Excel format. Figure 6-17 Two-winding transformer test preparation with CPC Editor Figure 6-18 10 kV results for a two-winding transformer (50 Hz) 6.2.3 Auto-Transformer The auto-transformer has only one winding with a tap for the low-voltage output.

  • Page 88: Reactors

    CP TD1 Reference Manual V 1.44 6.2.4 Reactors Similar to the auto-transformers, reactors also normally have only one winding. Often the low-voltage ends of the three phases are connected outside the tank to the Neutral. In this case we have 2 bushings per phase, which have to be connected for the DF test.

  • Page 89: Capacitance Measurement

    Power Transformers For oil paper insulation, the range of the DF values for new and aged transformers are published in some standards like [3.4] and in other literature [3.1], [3.2]. In IEEE Std. 62-1995 [3.1] the following limits for DF values are given: Table 6-4 DF values for oil paper insulation...
  • Page 90 CP TD1 Reference Manual V 1.44 [3.3] US Bureau of Reclamation: "Transformer Maintenance", Facility instructions, standards and techniques - Vol. 3-30, 2000 [3.4] ANSI Standard 62-1995: "IEEE Guide for Diagnostic Field testing of Electric Power Apparatus - Part 1: Oil Filled Power Transformers, Regulators, and Reactors", IEEE New York,...

  • Page 91: Capacitance And Df Measurement On High-Voltage Bushings

    Capacitance and DF Measurement on High-Voltage Bushings Capacitance and DF Measurement on High-Voltage Bushings Introduction High-voltage bushings are essential parts of power transformers, circuit breakers and of other power apparatus. More than 10% of all transformer failures are caused by defective bushings [4.2]. Although the price for a bushing is low compared to the costs of a complete transformer, a bushing failure can damage a transformer completely.
  • Page 92 CP TD1 Reference Manual V 1.44 Testing and maintaining high-voltage bushings are essential for continued successful operation of transformers and circuit breakers. Power outages may occur as the result of a bushing failure. High-voltage bushings used on transformers and breakers exist in many forms, including:...
  • Page 93 Capacitance and DF Measurement on High-Voltage Bushings Notes: – Equal capacitances, C through C , procedure equal distribution of voltage from the energized center conductor to the grounded condenser layer and flange. – The tap electrode is normally grounded in service except for certain designs and bushings used with potential device.

  • Page 94: Bushing Troubles

    CP TD1 Reference Manual V 1.44 Oil-filled A bushing where the space between the major insulation or the conductor, and the inside surface of a protective weather casing is filled with insulating oil. Oil-immersed A bushing composed of major insulators that are totally immersed in a bath of insulating oil.
  • Page 95 Capacitance and DF Measurement on High-Voltage Bushings Table 7-1 Bushing faults, part 1 [4.3] Failure Possible results Methods of detection Cracked porcelain Moisture enters; Visual inspection; Oil and/or gas leaks; Power factor test; Filler leaks out Hot-collar test Deterioration of Moisture enters;...

  • Page 96: Capacitance And Df Measurement On High-Voltage Bushings

    CP TD1 Reference Manual V 1.44 Table 7-1 Bushing faults, part 1 [4.3] Failure Possible results Methods of detection Lightning Cracked or broken Visual inspection; porcelain; Test lightning arresters Complete failure Corona Internal breakdown; Power factor test; Radio interference; Hot-collar test;...

  • Page 97: Ungrounded Specimen Test (Ust)

    Capacitance and DF Measurement on High-Voltage Bushings Note: Large variations in temperature significantly affect dissipation factor readings on certain types of bushings. For comparative purposes, readings should be taken at the same temperature. Corrections should be applied before comparing readings taken at different temperatures. Bushings may be tested by one or more of four different methods, depending upon the type of bushing and the dissipation factor test set available.
  • Page 98 CP TD1 Reference Manual V 1.44 be made on the insulation between the tap and the flange. Most manufacturers list the UST dissipation factor and capacitance values on the bushing nameplate. IN A IN B Equalizers C1 Layer Voltage tap...

  • Page 99: Grounded Specimen Test (Gst)

    Capacitance and DF Measurement on High-Voltage Bushings appendix or as recommended by the bushing manufacturer. The dissipation factor value of the dissipation factor tap insulation for most of the bushings discussed earlier is generally in the order of 1.0 percent or less. IN A IN B Equalizers...
  • Page 100 CP TD1 Reference Manual V 1.44 used to test bushings in apparatus when the three tests are either inapplicable or impractical, such as, with SF6 bushings. Perform a hot-collar test at every third skirt on SF6 bushings. Hot-collar tests are effective in locating cracks in...
  • Page 101 Capacitance and DF Measurement on High-Voltage Bushings tested near freezing where a large (greater than 1.00) correction may cause the result to be unacceptably high; in this case the equipment should be retested at a higher temperature. Bushing should not be tested when their temperatures are much below freezing because moisture may have changed to ice, which has a significantly higher volumetric resistivity any therefore be undetected.
  • Page 102 CP TD1 Reference Manual V 1.44 This connection technique is also very useful when the insulation of cables is measured. When transformer bushings are tested, inputs A and B can be used to measure two bushings at a time without rewiring:...
  • Page 103 Capacitance and DF Measurement on High-Voltage Bushings 0.51% 0.50% 0.49% 0.48% 0.47% 0.46% 0.45% 0.44% 0.43% 0.0Hz 100Hz 200Hz 300Hz 400Hz 500Hz Figure 7-9 Frequency scan of an aged RIP bushing 0.67% 0.66% 0.65% 0.64% 0.63% 0.62% 0.61% 0.60% Figure 7-10 Frequency scan of an OIP bushing (Phase A and B)

  • Page 104: Interpretation Of Measurement Results

    CP TD1 Reference Manual V 1.44 Interpretation of Measurement Results In the appendix typical DF values and limits are listed. Figures 7-11 and 7-12 show the aging of RBP, RIP and OIP bushings [4.5]. 40 years Figure 7-11 Aging of RBP, RIP and OIP bushings (change of capacitance)
  • Page 105 Capacitance and DF Measurement on High-Voltage Bushings 40 years Figure 7-12 Aging of RBP, RIP and OIP bushings (change of DF) RBP bushings show a significant change of capacitance and dissipation factor. In [4.6] RBP, RIP and OIP bushings were analyzed over more than 30 years (Figures 7-13 and 7-14).
  • Page 106 CP TD1 Reference Manual V 1.44 Limits for RBP Bushings High Limit 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 Years of operation time under oil Figure 7-13 Limits for RBP bushings Limits of Tan Delta...

  • Page 107: References

    Capacitance and DF Measurement on High-Voltage Bushings General guidelines for evaluating the C capacitance data are as follows: Table 7-2 General guidelines for evaluating the C1 capacitance data Δ C = C Evaluation: measured ΔC < 5% Acceptable 5% < Δ C < 10% Should be investigated ΔC >...
  • Page 108 CP TD1 Reference Manual V 1.44 [4.6] Seitz, V.: Vorbeugende Instandhaltung an Leistungstransformatoren – Betriebsbegleitende Messungen an Stufenschaltern und Durchführungen, OMICRON Anwendertagung 2003, Friedrichshafen...

  • Page 109: Capacitance And Df Measurement Of Generators And Motors

    Capacitance and DF Measurement of Generators and Motors Capacitance and DF Measurement of Generators and Motors The DF - voltage characteristic (power- factor tip-up) of stator windings is used primarily as a quality-control criterion in manufacturing high-voltage generators and motors. It is sometimes used as an acceptance test on individual coils. DF tip-up has been used as a maintenance test because a change in the tip-up value over a period of time is an indication of change of condition of the coil insulation.
  • Page 110 CP TD1 Reference Manual V 1.44 The maximum output power of the CP TD1 is 3600 VA, that means, capacitance values up to 80nF (50Hz) respectively 66nF (60Hz) can be measured. Bigger capacitors can be tested at lower voltages, or with a reactor switched in parallel to the capacitance of test object.

  • Page 111: Capacitance And Df Measurement Of Circuit Breakers

    Capacitance and DF Measurement of Circuit Breakers Capacitance and DF Measurement of Circuit Breakers Introduction The most common types of Circuit-Breakers (CB) are: • Oil Circuit-Breakers (OCB's) in dead tank design • Oil poor Circuit Breakers in life tank design •...

  • Page 112: Oil Poor Circuit Breakers (Live Tank)

    CP TD1 Reference Manual V 1.44 Test Connections There are six overall tests performed when the breaker is open. Each bushing is individually tested in the overall GST test mode. Three overall tests are performed with the breaker closed in the GST test mode. If the bushing is...

  • Page 113: Air Magnetic Circuit Breakers

    Capacitance and DF Measurement of Circuit Breakers Charging currents are expected to be small. Under dry ambient conditions, power factor results will be small and dielectric losses close to zero. Higher than normal UST measurement could be due to a defective vacuum bottle allowing moisture to enter or surface leakage across the vacuum housing.
  • Page 114 CP TD1 Reference Manual V 1.44...

  • Page 115: Capacitance And Df Measurement Of Overvoltage Arresters

    Capacitance and DF Measurement of Overvoltage Arresters Capacitance and DF Measurement of Overvoltage Arresters The purpose of a surge (lighting) arrester is to limit the over voltages that may occur across transformers and other electrical apparatus due either to lightning or switching surges.
  • Page 116 CP TD1 Reference Manual V 1.44 DF (f) 10.0% 9.0% 8.0% 7.0% 6.0% 5.0% 4.0% 3.0% 2.0% 1.0% 0.0% 0.0Hz 100Hz 200Hz 300Hz 400Hz Figure 10-1 Lightning arrester DF (f)
  • Page 117 Capacitance and DF Measurement of Overvoltage Arresters C (f) C in F 4.85x10 4.80x10 4.75x10 4.70x10 4.65x10 4.60x10 4.55x10 4.50x10 4.45x10 4.40x10 4.35x10 4.30x10 0.0Hz 100Hz 200Hz 300Hz 400Hz f in Hz Figure 10-2 Lightning arrester C (f)
  • Page 118 CP TD1 Reference Manual V 1.44 Rp (f) Ω Rp in 14.0x10 12.0x10 10.0x10 8.0x10 6.0x10 4.0x10 2.0x10 0.0Hz 100Hz 200Hz 300Hz 400Hz f in Hz Figure 10-3 Lightning arrester Rp (f)

  • Page 119: Technical Data

    Technical Data Technical Data 11.1 Technical Data of the CP TD1 in Combination with the CPC 100 11.1.1 High-Voltage Output Conditions: Signals below 45Hz with reduced values possible. Capacitive linear loads. Terminal U / f High volt. 10 ... 12kV AC <...
  • Page 120 CP TD1 Reference Manual V 1.44 f0 ± 10Hz 1.2s > 110dB at fx = f0 ± (10Hz or more) f0 ± 20Hz 0.9s > 110dB at fx = f0 ± (20Hz or more) Test current (RMS, selective) Terminal Range...
  • Page 121 Technical Data ϕ Power factor PF (cos Range Resolution Typ. accuracy Conditions error < 0.1% of reading f = 45 ... 70Hz, 0 ... 10% 5 digits I < 8mA, + 0.005% (capacitive) Vtest = 300V ... 10kV error < 0.5% of reading Vtest = 300V ...
  • Page 122 CP TD1 Reference Manual V 1.44 Weight and dimensions Weight Dimensions (W x H x D) CP TD1 test set 25kg 450 x 330 x 220mm (55.2lbs) (17.7 x 13 x 8.7") without handles 38.1kg 700 x 500 x 420mm test set &...

  • Page 123: Environmental Conditions

    Technical Data 11.2 Environmental Conditions Table 11-1 Climate Characteristic Rating Temperature Operating –10…+55 ºC (+14…+131 ºF) Storage and –20…+70 ºC (–4…+158 ºF) transportation Max. altitude 2000 m Relative humidity 5…95%; no condensation Tested according to IEC 60068-2- Table 11-2 Shock, Vibration, Noise Immunity Characteristic Rating Shock...

  • Page 124: Ce Conformity And Safety Standards

    EN 61326-1 International IEC 61326-1 Certified Safety Standards Europe EN 61010-1 International IEC 61010-1 UL 61010-1 11.4 Cleaning Warning: Prior to cleaning disconnect the CP TD1. To clean the CP TD1, use a cloth dampened with isopropanol alcohol or water.

  • Page 125: Accessories

    11.5 Accessories 11.5.1 Cables and Clamps The following accessories are delivered with the CP TD1: Accessories 1 High-voltage cable, triaxial, 20 m with cable drum 2 Low-voltage cables, coaxial, 20 m on one cable drum 2 Cables (1 × red, 1 × blue) for connecting low-voltage cable drum with...

  • Page 126: Optional Accessories

    CP TD1 Reference Manual V 1.44 11.5.2 Optional Accessories TH 3631 Temperature and Humidity Meter Use the optional device TH 3631 to measure ambient temperature, the test object temperature and humidity. Once these values were measured, enter them into the respective entry fields of the TanDelta test card’s Settings Page at "Compensations"...

  • Page 127: Ordering Information

    Temperature range –50…+150ºC (–58…302 F) Cable length 11.6 Ordering Information For ordering information on the CP TD1 and accessories, see the table below. Equipment description Article number CP TD1 TanDelta test set including software VE000640 (TanDelta test card), accessories and trolley &...
  • Page 128 CP TD1 Reference Manual V 1.44...

  • Page 129: Appendix

    Appendix Appendix 12.1 Parallel and Serial Equivalent Circuit Diagrams The dielectric losses in insulation can be presented in parallel and serial diagrams. The real situation is much more complicated and always is a mixture of an assortment of both diagram types. A parallel can be recalculated into a serial one and vice versa by using the following formulas.

  • Page 130: Negative Df Measurements

    CP TD1 Reference Manual V 1.44 12.2 Negative DF Measurements --------------------------------------------------- - -------- -------- -------- … 1n-1 Surface current Measuring tap ≈ 0Ω Bushing × ---------------------------------- - -- - jωC ------------------------- - jωC...
  • Page 131 Appendix × -------------------------------------------------------     ---------------- - -------- - –     RωC     ---------------- - -------- -     RωC × ---------------------------------------------------------- -     ---------------- - -------- - ...

  • Page 132: Two- And Three-Winding Transformer Tests (Ieee C57.12.90)

    CP TD1 Reference Manual V 1.44 12.3 Two- and Three-Winding Transformer Tests (IEEE C57.12.90) Method I Method II Test without guard circuit Test with guard circuit Two-winding transformers Two-winding transformers High to low and ground High to low and ground...

  • Page 133: Limits For Test Voltages For C2 Testing On Bushings

    Appendix an electrical instrument or measuring circuit to divert unwanted currents from the measuring means. Permanently connected windings, such as in autotransformers or regulators, shall be considered as one winding. 12.4 Limits for Test Voltages for C2 Testing on Bushings Manufacturer Bushing Type or Class Test Voltage...

  • Page 134: Introduction

    CP TD1 Reference Manual V 1.44 capacitance in condenser bushings. It describes the constructional/design differences between C1 and C2 and discusses the factors that can influence these measurements. 12.5.2 Introduction C2 power factor and capacitance measurement of condenser bushings has been a topic of much discussion for many years.
  • Page 135 Appendix the voltage tap can be used for measuring the power factor and capacitance of C1 and C2 insulation of the bushing. In addition, this tap can be used for monitoring the partial discharge during factory tests and insulation leakage current (including partial discharge) during field service operation.

  • Page 136: Factors Affecting C1, C2 Capacitance And Power Factor Measurements

    CP TD1 Reference Manual V 1.44 C2 insulation of the bushing. In addition, this tap is sometimes used for monitoring the partial discharge during factory tests and insulation leakage current (including partial discharge) during field service operation. See Figure 12-3 for condenser design and test tap details.
  • Page 137 Appendix IEEE Standard C57.19.01 specifies a limit 0.5% for C1 power factor for oil impregnated paper insulated bushings, Type O Plus C, AB, and T condenser bushings C1 power factor values are well below this limit. Condenser bushings rated 69 kV and below as mentioned earlier, have the main C1 capacitance, which is strictly controlled by design.
  • Page 138 CP TD1 Reference Manual V 1.44 between the C1 layer/foil and the surrounding materials, as shown by patterned areas in Figure 12-4. Depending upon the design, the C2 power factor of these bushings can range from 0.1% to 2%. Paper...
  • Page 139 Appendix TYPE / STYLE -> AB / B035200AA AB / B035200AA T / 025V1000VY T / 025V1000VY C1 / C2 PF % C1 / C2 CAP pF C1 / C2 PF % C1 / C2 CAP pF NP Values 0.29 / 0.11* 508 / 494* 0.28 / 0.64** 1112 / 306**...

  • Page 140: Conclusions

    CP TD1 Reference Manual V 1.44 Due to design and construction, the C2 power factor of condenser bushings rated 69 kV and below may therefore exceed the C1 power factor limit of 0.5 % specified in the IEEE Standard. The IEEE Standard does not specify any limit for C2 power factor.

  • Page 141: Biography

    Appendix design. The initial test values before installation should be compared with the factory nameplate values. While checking the power factor and capacitance values of these bushings, it is important to compare the field test values with the initial benchmark value after installation. Any significant deviation from the benchmark value would be a cause for concern and should be investigated.

  • Page 142: Df Limits Of Rbp Bushings (Micafil Ag)

    CP TD1 Reference Manual V 1.44 12.6 DF Limits of RBP Bushings (Micafil AG) Limits are reached in approximately 25 years. Not valid for humid insulators. a) Limits of the dissipation factor at 20°C: U rated [kV] DF (%) 1.15 b) Limits of the capacitance change (Delta C) at 20°C...

  • Page 143: Df Limits Of Bushings (B)

    Appendix 12.7 DF Limits of Bushings (B) Manufacturer Bushing Type or Initial P.F. for Dangerous Class P.F. value at bushings, at 20 x C (%) General Electric 10.0 12.0 Lapp bushings 0.7 - 1.2 Ohio Brass ODOF manufactured prior to 1 - 10 Initial P.F.

  • Page 144: Df Limits Of Bushings (C)

    CP TD1 Reference Manual V 1.44 12.8 DF Limits of Bushings (C) Manufacturer: Bushing Power Factor Limits Type or Class (% at 20°C) Description Typical Doubtful or questionable ASEA Brown Boveri (ABB) Double name- plate Note: 1. Contact manufacturer if capacitance increases to 110% of original installed value 2.
  • Page 145 Appendix Manufacturer: Bushing Power Factor Limits Type or Class (% at 20°C) Description Typical Doubtful or questionable General Electric: Through Porcelain High Current, Solid Porcelain 12.0 Flexible Cable, Compound Filled Oil-Filled Upper Portion, Sealed Oil-Filled, Sealed Oil-Filled Upper Portion, Sealed Oil-Filled Upper Portion, Sealed Oil-Filled Expansion Chamber Forms C &...

  • Page 146: Transformer Diagnosis

    CP TD1 Reference Manual V 1.44 Manufacturer: Bushing Power Factor Limits Type or Class (% at 20°C) Description Typical Doubtful or questionable Lapp: Paper Oil Condenser type; POC & PA Totally Enclosed, 23-69kV Paper Resin Condenser PRC & PRC-A Core Paper Epoxy hard core type;...

  • Page 147: Introduction

    Appendix 12.9.1 Introduction Due to ever-increasing pressure to reduce costs, the power industry is forced to keep old power facilities in operation as long as possible. In most European countries, about one third of the transformers are older than 30 years. Transformers, which are older than 50 years can still be found in service [1].
  • Page 148 CP TD1 Reference Manual V 1.44 Figure 12-6 Transformer fault due to a defective bushing The most frequent sources of failure are the tap changers, bushings, the paper- oil insulation and the accessory equipment (Figure 12-7). Figure 12-7 Sources of transformer faults...

  • Page 149: Methods Of Analysis

    Appendix 12.9.2 Methods of Analysis One of the most important and proven methods is Dissolved Gas Analysis (DGA). The hydrocarbon gases dissolved in the oil allow conclusions to be made about the condition of the transformer and specific faults by investigating changes of the gas composition [4], [5], [6], [7].

  • Page 150: Fault Localization

    CP TD1 Reference Manual V 1.44 12.9.3 Fault Localization In order to find out the reason for high gas values, further tests have to be performed for the transformer. Common test methods are: • Winding resistance measurement • On-Load Tap Changer (OLTC) test •...

  • Page 151: Winding Resistance Measurement And On-Load Tap Changer Test

    Appendix frequencies different from the line frequency and their harmonics, together with measurements using selective filtering techniques, the test equipment can be operated on-site, even in substations with high electromagnetic disturbances. 12.9.4 Winding Resistance Measurement and On-Load Tap Changer Test Winding resistances are tested in the field to check for loose connections, broken strands and high contact resistance in tap changers.
  • Page 152 CP TD1 Reference Manual V 1.44 In most cases, the tap changer consists of two units. The first unit is the tap selector, which is directly located inside the transformer tank and switches to the next higher or lower tap without carrying current. The second unit is the diverter switch, which switches without any interruption from one tap to the next while carrying load current.
  • Page 153 Appendix Figure 12-12 shows a diverter switch of a 40 MVA transformer for 110 kV. The switches shown are positioned near the star-point of the transformer's high- voltage windings. Figure 12-11 Transformer with tap changer...
  • Page 154 CP TD1 Reference Manual V 1.44 Figure 12-12 Diverter switch for 110 kV/40 MVA...

  • Page 155: Four-Wire Connection For Transformer Winding Resistance Measurement

    Appendix 12.9.5 Four-Wire Connection for Transformer Winding Resistance Measurement Since the winding resistances are very small, the test set is connected in 4-wire configuration. It has to be observed that the contact resistances of the connection clamps do not falsify the measuring result (Figure 12-13). Measuring lines for U Measuring...

  • Page 156: Safety Aspects

    CP TD1 Reference Manual V 1.44 x = reference temperature --------------------- - × m = temperature at measurement Figure 12-14 Automatically generated test report Even comprehensive measurements can be performed very efficiently within a short time. For example, if all resistances of the taps 1 - 19 upwards and the taps 19 - 1 downwards for all three phases are measured, this corresponds to a total of 114 resistance measurements.

  • Page 157: Delta-Connected Windings

    Appendix 12.9.7 Delta-Connected Windings For delta-connected windings, R12, R23 and R31 cannot be measured directly but calculated from the measured Ra, Rb and Rc values. Ra = R1 + R2 Rb = R2 + R3 Rc = R3 + R1 Y connection without Neutral: ...

  • Page 158: Winding Resistance Measurement Of A 100 Mva Transformer

    CP TD1 Reference Manual V 1.44 12.9.8 Winding Resistance Measurement of a 100 MVA Transformer The 220 kV/110 kV – 100 MVA transformer under test manufactured in 1995 was found to have conspicuously high quantities of gas in the oil, from which the conclusion was drawn of inner overheating.
  • Page 159 Appendix high contact resistances are actually caused by the switching contacts of the tap selector. No silver-plated contacts were originally used and the copper contact surface was now coated by oil carbon (Figure 12-17) [2]. Figure 12-17 Bad tap selector...
  • Page 160 CP TD1 Reference Manual V 1.44 After a full maintenance of the tap selector, no significant difference to the values measured at the factory in 1954 could be observed (Figure 12-18). Figure 12-18 Resistance after maintenance To examine the results in more detail, it is recommended to graph the difference between "UP"...
  • Page 161 Appendix incomplete, with potentially serious consequences. To undertake a complete test to record the values for all taps with the described test equipment is not a significant effort. Figure 12-19 Difference "UP" - "DOWN"...

  • Page 162: Dynamic Behavior Of The Diverter Switch

    CP TD1 Reference Manual V 1.44 12.9.9 Dynamic Behavior of the Diverter Switch To date, only the static behavior of the contact resistances has been taken into account in maintenance testing. With a dynamic resistance measurement, the dynamic behavior of the diverter switch can be analyzed.

  • Page 163: 12.9.10 Turns Ratio

    For a more detailed analysis, a transient recorder can be used to record the current curve in real time. For this measurement, the transient recording functionality of the OMICRON CMC 256 was used (Figure 12-20). 12.9.10 Turns Ratio This test is normally only performed if a problem is suspected from the DGA, dissipation factor test or relay operation.
  • Page 164 CP TD1 Reference Manual V 1.44 In the Figures 12-21 and 12-22, an analysis of a transformer with shorted turns in the low-voltage winding (Phase A) is shown. Figure 12-21 Ratio magnitude = f(f) Figure 12-22 Ratio phase angle = f(f)

  • Page 165: 12.9.11 Excitation Current

    Appendix The large difference of approximately 20% indicates a failure with 20% of the turns. Due to the non-linear behavior, it can be assumed that the current, which is flowing through the low-voltage winding is partly flowing through the magnetic core.

  • Page 166: 12.9.12 Leakage Reactance

    CP TD1 Reference Manual V 1.44 to fingerprints is recommended. If no such test results are available, comparison should be made to transformers of similar design. On three-phase transformers, results are also compared between phases. On a three-phase, y-delta or delta-y transformer, the excitation current will be higher on the two outer phases than on the middle phase.
  • Page 167 Appendix years later. Leakage reactance testing is performed by short-circuiting the low- voltage winding, and applying a test voltage to the high-voltage winding (Figure 12-24). Figure 12-24 Short-circuit impedance test Changes in leakage reactance and observed in capacitance tests (explained later) serve as an excellent indicator of winding movement and structural problems (displaced wedging, buckling, etc.).
  • Page 168 CP TD1 Reference Manual V 1.44 The transformer with the shorted LV winding (Figure 12-21 and 12-22), was used for the leakage reactance frequency scan (Figure 12-25). The faulty phase shows a totally different behavior. As already mentioned a part of the LV winding current is flowing through the core.

  • Page 169: 12.9.13 Capacitance And Df Measurement

    Appendix 12.9.13 Capacitance and DF Measurement Capacitance (C) and Dissipation Factor (DF) measurement is an established and important insulation diagnosis method which was first published by Schering in 1919 [9] and utilized for this purpose in 1924. In a simplified diagram of the insulation C represents the capacitance and Rp the losses (Figure 12-26).
  • Page 170 CP TD1 Reference Manual V 1.44 The vector diagram of the system is shown in Figure 12-27. ---------- - ------------------- - δ 1 ωC × with ω 2 π f × × and f frequency δ Definition of dissipation factor (tan δ) and the vector diagram...
  • Page 171 Appendix The first measuring device for tan delta was the mentioned Schering bridge [9] (Figure 12-28). ------------ - ----- - jωC jωC ------------------------- ------------------------- jωC Figure 12-28 Schering bridge  Real parts: ----- - ----- - × ----- - Imaginary parts: ...
  • Page 172 CP TD1 Reference Manual V 1.44 In Figure 12-28, the serial connected C1 and R1 represent the test object with losses, C2 the loss-free reference capacitor. The parallel circuit diagram in Figure 12-26 can be transferred as a direct equivalent into this serial diagram at specified frequencies.
  • Page 173 Appendix for them electronically, so it is now for the first time possible to measure in the field down to DF = 5 x 10 E-5. The correlation between DF and power factor = cos ϕ and the vector diagram are shown in Figure 12-30. Withδ...

  • Page 174: 12.9.14 Df Measurements On Transformer Windings

    CP TD1 Reference Manual V 1.44 12.9.14 DF Measurements on Transformer Windings A transformer contains a complicated insulation system. High- and low-voltage windings have to be insulated to tank and core (ground) and against each other. All these insulation gaps should be checked regularly.

  • Page 175: 12.9.15 Capacitance Measurements On Transformer Windings

    Appendix The DF value for 60Hz is about 0.30%. The character of the DF curve over the frequency range is interesting and should be retained as a fingerprint result for future diagnosis of the insulation and its degradation. Figure 12-32 Frequency scan HV-LV (154 kV-20 kV) 12.9.15 Capacitance Measurements on Transformer Windings The capacitance test measures the capacitance between the high- and low-...
  • Page 176 CP TD1 Reference Manual V 1.44 Figure 12-33 shows the change of C1 for different types of bushings: • "Resin-impregnated paper (RIP) • "Oil-impregnated paper (OIP) and • "Resin-bonded paper (RBP). 40 years Figure 12-33 Aging of RBP, RIP and OIP bushings (change of capacitance)
  • Page 177 Appendix 40 years Figure 12-34 Aging of RBP, RIP and OIP bushings (change of DF) To determine bushing losses, dissipation factor tests are also performed. Figure 12-34 shows the increase of losses for RIP-, OIP-, and RBP-bushings. RBP- bushings particularly show a significant change of capacitance and dissipation factor during their life-time [10].
  • Page 178 CP TD1 Reference Manual V 1.44 About 90% of bushing failures may be attributed to moisture ingress. As already shown with the winding-to-winding insulation, analysis of bushing insulation is much more detailed when frequency scans are performed. Figures 12-35 to 12-37 show interesting DF curves of power transformer HV bushings over frequency.

  • Page 179: Summary

    Appendix Figure 12-37 DF of an OIP 154 kV bushing (1970) These results show that the frequency scan method will enable more detailed insulation analysis in the future. But it is necessary to compare the curves to fingerprint measurements. This way it will be possible to detect changes in insulation at a very early stage.

  • Page 180: 12.10 References

    CP TD1 Reference Manual V 1.44 12.10 References Weck, K.-H.: Instandhaltung von Mittelspannungs-verteilnetzen, Haefely Symposium 2000, Stuttgart Seitz, V.: Vorbeugende Instandhaltung an Leistungstransformatoren – Betriebsbegleitende Messungen an Stufenschaltern und Durchführungen, OMICRON Anwendertagung 2003, Friedrichshafen CIGRE-WG 12-05: An international survey on failures in large power transformers in service, Electra No.

  • Page 181: Temperature Correction Factors

    Appendix 12.11 Temperature Correction Factors The temperature curves can be used in the TanDelta test card (see 3.4 ”TanDelta Test Card - Settings Page (2/2)” on page 30). × PF DF PF DF where PF(DF) is the corrected Power Factor (Dissipation Factor) to 20 °C PF(DF) is the Power Factor (Dissipation Factor) measured at T k is the correction factor...

  • Page 182: 12.11.2 Bushings

    CP TD1 Reference Manual V 1.44 12.11.2 Bushings The temperature curves apply to medium-aged bushings and are determined by long-time studies of a utility. Resin Impregnated Paper (RIP) Temperature in °C Resin Bonded Paper (RBP) Temperature in °C...
  • Page 183 Appendix Oil Impregnated Paper (OIP) Temperature in °C...
  • Page 184 CP TD1 Reference Manual V 1.44...

  • Page 185: Omicron Service Centers

    Oberes Ried 1 A-6833 Klaus, Austria Phone: +43 5523 507-333 Fax: +43 5523 507-999 support@omicron.at www.omicron.at For addresses of OMICRON electronics offices with customer service centers, regional sales offices or offices for training, consulting and commissioning please visit our Web site.
  • Page 186 CP TD1 Reference Manual V 1.44...

  • Page 187: Index

    CP CAL1 calibration set ....23 CP TD1 ......127 CP TD1 TH 3631 .
  • Page 188 ..... . . 11 weight CP TD1 ......122...

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