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Capacitance and Dissipation Factor Measurement

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.

Figure 5-13

Temperature behavior of silicon liquid [2.3]

2.18

2.42

2.70

3.00

Table 5-1

Temperature correction factor for mineral oil insulation [2.4]

Test temperature

(°C)

Correction Factor

0.1

0.01

Specific volume resistan

°C

tan

1,2

Summary of Contents for CP TD1

Page 1: ...CP TD1 Reference Manual...

Page 2: ...al data embodied in this manual represent the technical status at the time of writing and are subject to change without prior notice We have done our best to ensure that the information given in this...

Page 3: ...ith Trolley 21 2 1 2 Setup of Devices without Trolley 21 2 2 CP TD1 Connected to a Test Object 22 2 3 CP TD1 Connected to CP CAL1 23 2 4 Calibrating the CP TD1 Using a Reference Capacitor 23 2 4 1 Cal...

Page 4: ...ement 89 6 5 References 89 7 Capacitance and DF Measurement on High Voltage Bushings 91 7 1 Introduction 91 7 2 Types of Bushings 91 7 3 Bushing Troubles 94 7 4 Capacitance and DF Measurement on High...

Page 5: ...mits for Test Voltages for C2 Testing on Bushings 133 12 5 C2 Measurement on High Voltage Bushings 133 12 5 1 Abstract 133 12 5 2 Introduction 134 12 5 3 Design Construction of C1 and C2 Capacitance i...

Page 6: ...2 Leakage Reactance 166 12 9 13 Capacitance and DF Measurement 169 12 9 14 DF Measurements on Transformer Windings 174 12 9 15 Capacitance Measurements on Transformer Windings 175 12 9 16 Capacitance...

Page 7: ...regulations relevant to working on power transformers Operator Qualifications and Safety Standards Working on high voltage assets can be extremely dangerous Testing with the CP TD1 must be carried out...

Page 8: ...rve the five safety rules Disconnect completely Secure from reconnection Verify that the installation is dead Carry out grounding and short circuiting Provide protection against adjacent live parts Sy...

Page 9: ...nics are authorized to operate the CP TD1 Before starting the work clearly establish the responsibilities Personnel receiving training instructions directions or education on the CP TD1 must be under...

Page 10: ...CP TD1 Reference Manual V 1 44 10 Figure 1 1 Example for the separation of safe and high voltage area using different OMICRON electronics devices Safe area High voltage area...

Page 11: ...f the CP TD1 completely before you connect or disconnect any cable disconnect the CPC 100 from mains or press its Emergency Stop button The high voltage cable must always be well attached and tightly...

Page 12: ...he plugs by turning them until you feel a stop Note Tighten the plugs manually Do not use any tools for that because that can damage the plugs or connectors Do not use any other cables than the ones s...

Page 13: ...atus 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 ref...

Page 14: ...CP TD1 Reference Manual V 1 44 14...

Page 15: ...ts of the capacitance Cx and the dissipation factor tan DF or power factor cos PF respectively Both the dissipation factor and the power factor grant information about possible losses in the insulatio...

Page 16: ...High voltage output with attached screw plug and yellow grounding plug Equipment trolley Booster cable CPC 100 CP TD1 short type Via this cable CPC 100 controls the CP TD1 output voltage CPC 100 CPC 1...

Page 17: ...he measuring cables Swivelling mounting brackets for the CPC 100 top and CP TD1 bottom To secure the CPC 100 while pulling the trolley a safety belt is available not shown Data cable CPC 100 CP TD1 sh...

Page 18: ...and Booster Input Figure 1 2 Grounding terminal and booster input of the CP TD1 1 3 2 Serial Interface Connector and Measuring Inputs Figure 1 3 Serial interface and measuring inputs of the CP TD1 Boo...

Page 19: ...Introduction 19 1 3 3 High Voltage Connector Figure 1 4 High voltage connector of the CP TD1 High voltage connector Grounding terminal...

Page 20: ...CP TD1 Reference Manual V 1 44 20...

Page 21: ...d screws to ensure a solid connection to the grounding terminals of all devices 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...

Page 22: ...CP TD1 Reference Manual V 1 44 22 2 2 CP TD1 Connected to a Test Object CP TD1 CPC 100 IN Ix Measurement PE 12 kV IN A IN B Power transformer Grounding terminal Booster Serial Safe area HV area...

Page 23: ...acitor By connecting a reference capacitor e g optional device CP CAL1 with known values of capacity Cref and dissipation factor DFref in mode UST A the values Cx and DFx can be measured and then comp...

Page 24: ...t xml file Note If you change the factory made calibration the responsibility for the accuracy of the CP TD1 will be in your hands 2 4 1 Calibration Tips For calibration set the averaging factor to ma...

Page 25: ...ear for no assessment Enter the nominal values in the entry fields here Cref and DFref availability and naming depend on the measuring mode These values serve as reference for the assessment Their tol...

Page 26: ...Double entries are rejected If you need identical test points for an increasing and a decreasing voltage ramp set values very close to each other e g 2000V and 2001V The CP TD1 then puts out the speci...

Page 27: ...Test Cards 27 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: ...e option use default frequency of xx xx Hz is not specifically selected 5Hz means that interferences at frequencies with an offset of 5Hz from the measuring frequency will not affect the results The s...

Page 29: ...on TanDelta and press E D I T C A L I B to enable the entry fields Cx correction factor for Cmeas multiplier DF PF corrective value added to dissipation or power factor can be or Note You must enter y...

Page 30: ...the measurement takes place in oil or air determines the k factor A N S I C 5 7 1 2 The oil temperature is the determining medium for the k factor Bushings The air temperature at the respective bushi...

Page 31: ...plates are predefined test procedures often with comments that run on the CPC 100 and guide your through the test Once completed the XML file is saved downloaded to the PC and then loaded into the cor...

Page 32: ...CP TD1 Reference Manual V 1 44 32...

Page 33: ...ights 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 button is required 4 2 Connectio...

Page 34: ...voltage output At the CP TD1 press the high voltage cable s plug to the connector tightly and turn the screw cap manually without using any tools until you feel a mechanical stop If you notice a rough...

Page 35: ...3 The green warning light O lights up showing that the CPC 100 output does not carry a dangerous voltage or current yet Note If none or both warning lights are on the unit is defective and must not be...

Page 36: ...he CPC 100 outputs are not activated 2 Press the Emergency Stop button on the CPC 100 front panel Warning If you have a cardiac pacemaker do not use the CP TD1 Before operating the CP TD1 make sure th...

Page 37: ...key to avoid anybody accidentally turning on the high voltage 4 Plug off the high voltage cable from the high voltage output of the CP TD1 5 Disconnect the cables from the CP TD1 Warning Earth connec...

Page 38: ...CP TD1 Reference Manual V 1 44 38...

Page 39: ...Aging of insulation Contamination of insulation liquids with particles Water in solid and liquid insulation Partial discharges 5 1 Theory In an ideal capacitor without any dielectric losses the insul...

Page 40: ...igure 5 1 Losses can also be represented by serial equivalent circuit diagram with Cs and Rs chapter 12 1 The definition of the dissipation factor and the vector diagram are shown in Figure 5 2 Figure...

Page 41: ...41 Capacitance and Dissipation Factor Measurement Figure 5 2 Definition of dissipation factor tan and the vector diagram Re IRp U ICp I jIm tan 1 RP CP...

Page 42: ...1 44 42 The correlation between the Dissipation Factor and Power Factor PF cos and the vector diagram are shown in Figure 5 3 Figure 5 3 Correlation between DF and PF Im ICN ICX UO Re With 1 cos tan...

Page 43: ...of conductive particles movement of ions and electrons polarization effects Figure 5 4 Figure 5 4 Kind of polarization Kind of polarization Suspension Rotation Electrons Ions Dipoles completely revers...

Page 44: ...nsion of electrons is completely reversible Figure 5 5 shows this mechanism This kind of polarization is also called Atom Polarization Figure 5 5 Polarization of electrons in the electrical field Figu...

Page 45: ...45 Capacitance and Dissipation Factor Measurement Figure 5 7 Polarization of dipoles in the electrical field without E with E...

Page 46: ...rotation along with the applied frequency causes the described losses Figure 5 8 Water molecule in the electrical field Additional losses are known as interfacial polarization Inter phase boundaries e...

Page 47: ...egion 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...

Page 48: ...dent on the water content 2 3 With low water content the breakdown voltage is very sensitive with higher water content the DF is a good indicator Figure 5 10 Breakdown voltage and DF in oil dependent...

Page 49: ...y of the oil decreases so the particles ions and electrons can move easier and faster Thus the DF increases with temperature 2 3 Figure 5 11 DF of new and aged oil dependent on temperature Dissipation...

Page 50: ...correction factor for mineral oil insulation 2 4 where Fp20 is the power factor corrected to 20 C Fpt is the power factor measured at T T is the test temperature C K is the correction factor Table 5...

Page 51: ...uid Other insulating liquids may have different correction factors Figure 5 13 Temperature behavior of silicon liquid 2 3 55 2 18 60 2 42 65 2 70 70 3 00 Table 5 1 Temperature correction factor for mi...

Page 52: ...00 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 The followi...

Page 53: ...to winding DF measurement oil paper DF f Figure 5 16 Frequency scan of a OIP bushing Phase A and B 0 55 0 50 0 45 0 40 0 35 0 30 0 25 0 0Hz 100Hz 200Hz 300Hz 400Hz 500Hz L f HL f H f 0 67 0 66 0 65 0...

Page 54: ...Delta Motor 6 kV Figure 5 17 Voltage scan of a 6 kV motor 5 2 Measurement of Capacitance and Dissipation Factor Power Factor Capacitance C and Dissipation Factor DF measurement was first published by...

Page 55: ...in Figure 5 1 can be transferred as a direct equivalent into this serial diagram at specified frequencies section 12 1 Figure 5 18 Schering bridge Real parts Imaginary parts C1 C2 R1 R3 R4 C4 R1 1 j C...

Page 56: ...measuring C and DF Cn is a gas insulated reference capacitor with losses below 10E 5 For laboratory use such capacitors are regularly used to obtain precise measurements as the ambient lab temperature...

Page 57: ...uring principle To the present day the dissipation or dissipation factor was measured only at line frequency With the power source described in 2 2 it is now possible to make these insulation measurem...

Page 58: ...se is drawn With a three phase transformer the equivalent circuit diagram is very similar because normally the phases of the high voltage H the low voltage L and the tertiary T windings are connected...

Page 59: ...ors are energized Only C1 is measured because the relay matrix only connects C1 to the measuring input instrument whereas the currents through C2 and C3 are bypassed C2 and C3 are connected to the foo...

Page 60: ...s 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 The capacitance value out...

Page 61: ...on Factor Measurement Now we want to measure C HL The connection diagram is shown in Figure 5 24 The measuring mode is UST A Figure 5 24 Measurement of C HL in UST A mode C HT and C H are guarded IN A...

Page 62: ...de 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 Only by connecting L to GUARD the current flowing to...

Page 63: ...partial capacitors inside Figure 5 26 Measurement of C H in GST gA B mode C HL and C HT are guarded 5 4 References IN A IN B CHL CHT CH GSTg A B C CH 2 1 Schering H Br cke f r Verlustmessungen T tigke...

Page 64: ...Reference Manual V 1 44 64 2 5 Seitz V Vorbeugende Instandhaltung an Leistungstransformatoren Betriebsbegleitende Messungen an Stufenschaltern und Durchf hrungen OMICRON Anwendertagung 2003 Friedrich...

Page 65: ...ons of hydrogen and hydrocarbon gases are found in the oil This way important preventative maintenance can be performed in time to avoid an unexpected total failure DGA analysis and interpretation of...

Page 66: ...te value of gas content are the quotients of the gas components which also allow for additional information Table 6 1 3 2 Table 6 1 Dissolved Gas Analysis 3 2 Type of fault PD Partial discharge 0 01 0...

Page 67: ...nt If C2H2 is being generated arcing is still going on CO will be present if paper is being heated High energy discharges arcing Metal fusion poor contacts in tap changer or lead connections Weakened...

Page 68: ...rges between clamping parts bushing and tank high voltage and ground within windings Tracking in wood blocks glue of insulating beam winding spacers Dielectric breakdown of oil load tap changer breaki...

Page 69: ...by comparing infrared scans of the top of a bushing with a sister bushing When loaded heat from a poor connection at the bottom will migrate to the top of the bushing which will display a markedly hi...

Page 70: ...acitance 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 m...

Page 71: ...utside connected Neutral have to be disconnected from ground tank 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 t...

Page 72: ...All tests should be made with oil temperatures near 20 C Temperature corrections can be calculated by using correction curves but they depend a great deal on the insulation material the water content...

Page 73: ...sible in this case When the load is unbalanced it is necessary for flux compensation in the three limbs of the core Figure 6 2 Three winding transformer with winding to winding and winding to ground c...

Page 74: ...ows the simplified circuit diagram of the three phase transformer of Figure 6 2 Figure 6 3 Three phase transformer with winding capacitances A Phase A B Phase B C Phase C H High Voltage winding C H Ca...

Page 75: ...s Figure 6 4 Three winding transformer test according to IEEE 62 1995 T Tertiary winding C T Cap T to Ground C H T Cap H to T Caution All phases and the neutral terminal of one winding H L and T have...

Page 76: ...r two and three winding transformers can be found in 3 6 This test procedure is included in the appendix and is now used as an example to show the test preparation of a 3 winding transformer test with...

Page 77: ...t 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 transform...

Page 78: ...CP TD1 Reference Manual V 1 44 78 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: ...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: ...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 instructi...

Page 81: ...or 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 instructi...

Page 82: ...Hz Figure 6 12 shows the results for 10 kV 1 H HL 2 H 3 HL 5 L LT 6 L 7 LT 9 T TH 10 T 11 TH In line 4 the difference of the capacity values of test 1 test 2 is calculated so it can be compared to tes...

Page 83: ...y 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 utilizi...

Page 84: ...CP TD1 Reference Manual V 1 44 84 Figure 6 14 Frequency scan for H L f 5 kV...

Page 85: ...dure for transformers with three windings Figure 6 15 shows the simplified circuit diagram of a two winding transformer Figure 6 15 Two winding transformer with winding capacitances H High Voltage win...

Page 86: ...inding transformer is shown according to IEEE 62 1995 3 4 Figure 6 16 Two winding transformer test according to IEEE 62 1995 Test Mode Energize Ground Guard UST Measure GST HIGH LOW CH GST LOW HIGH CL...

Page 87: ...on 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 Only one measure...

Page 88: ...rprint test values for future comparisons Periodic tests during the life cycle of the transformer can indicate that the insulation is aging normally or rapidly 6 4 1 Dissipation Factor Measurement Env...

Page 89: ...erve as an excellent indicator of winding movement and structural problems displaced wedging buckling etc If a winding damage is suspected then the capacitance measurement should be supplemented by a...

Page 90: ...r Diagnostic Field testing of Electric Power Apparatus Part 1 Oil Filled Power Transformers Regulators and Reactors IEEE New York 1995 3 5 US Bureau of Reclamation Transformer Diagnostics Facility ins...

Page 91: ...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 A regular capacitanc...

Page 92: ...and it is therefore the main one focused in this guide Cylindrical conducting layers are arranged coaxially with the conductor within the insulating material The length and diameter of the cylinders a...

Page 93: ...Impregnated Paper insulation RIP Oil Impregnated Paper insulation OIP Composite A bushing where the insulation consists of two or more coaxial layers consisting of different insulating materials Comp...

Page 94: ...ion Gas insulated A bushing that contains compressed gas like SF6 or mixtures of SF6 with other gasses i e N2 This type is frequently used for circuit breaker bushings 7 3 Bushing Troubles About 90 pe...

Page 95: ...ance Moisture in insulation Moisture enters Power factor test Hot collar test Solder seal leak Moisture enters Filler leaks out Visual inspection Power factor test Hot collar test Hot wire test for mo...

Page 96: ...ed values should be compared with previous tests and nameplate values Lightning Cracked or broken porcelain Complete failure Visual inspection Test lightning arresters Corona Internal breakdown Radio...

Page 97: ...thods are described as follows 7 5 Ungrounded Specimen Test UST This test measures the insulation between the center conductor and the capacitance tap the dissipation factor tap and or ungrounded flan...

Page 98: ...onductor and flange grounded The dissipation factor of a capacitance or potential tap will generally be of the order of 1 0 percent or less Routine tap insulation tests are not normally recommended fo...

Page 99: ...gs connected to de energized equipment spare bushings or bushings that have been isolated from connected windings and interrupters The test is performed by energizing the bushing conductor and groundi...

Page 100: ...eplate In such cases field measurement particularly UST should compare with the nameplate dissipation factors In general any bushing that exhibits a history of continuing increase in dissipation facto...

Page 101: ...lly with both nameplate and previous tests in assessing bushing condition This is especially important for capacitance graded bushings where an increase in capacitance of 5 more over the initial namep...

Page 102: ...Frequency scans of bushing insulation are helpful for a better diagnosis Figure 7 8 shows a frequency scan of a new RIP bushing Figure 7 9 of an aged one This additional information should be used as...

Page 103: ...of an aged RIP bushing Figure 7 10 Frequency scan of an OIP bushing Phase A and B 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 0 67 0 66 0 65 0 64 0 63 0 62 0 61 0...

Page 104: ...ypical DF values and limits are listed Figures 7 11 and 7 12 show the aging of RBP RIP and OIP bushings 4 5 Figure 7 11 Aging of RBP RIP and OIP bushings change of capacitance 10 8 6 4 2 0 10 8 6 4 2...

Page 105: ...gnificant 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 What is important are the curves for the upper limits...

Page 106: ...gure 7 14 RBP bushings Limits of Tan Delta 3 5 3 0 2 5 2 0 1 5 1 0 0 5 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 Years of operation time under oil Low High Limit TanDelta x 10 2 0 50 0 45 0 4...

Page 107: ...value for new bushing 4 1 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 1995 4 2...

Page 108: ...Reference Manual V 1 44 108 4 6 Seitz V Vorbeugende Instandhaltung an Leistungstransformatoren Betriebsbegleitende Messungen an Stufenschaltern und Durchf hrungen OMICRON Anwendertagung 2003 Friedrich...

Page 109: ...d of time is an indication of change of condition of the coil insulation With increasing test voltage Partial Discharges PD may occur This can be seen in Figure 8 1 The sensitivity of the power factor...

Page 110: ...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 In any case a f...

Page 111: ...breakers are composed of a steel tank filled with insulating oil A typical three phase oil circuit breaker has six bushings Three bushings channel the three phase line currents to a set of fixed conta...

Page 112: ...lize the voltage drop across the contacts if they are open These capacitors have to be removed when the oil quality in the chambers is tested The capacitance values of the described capacitors are imp...

Page 113: ...er or surface leakage across the vacuum housing Clean the surface of the vacuum bottle and retest Ensure that all cabinet heaters are working to maintain a sufficient temperature surrounding the vacuu...

Page 114: ...CP TD1 Reference Manual V 1 44 114...

Page 115: ...that serve as an insulator under normal conditions and as a conductor under over voltage conditions After an over voltage condition is cleared the arrester must return to its normal insulating conditi...

Page 116: ...CP TD1 Reference Manual V 1 44 116 DF f Figure 10 1 Lightning arrester DF f DF 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 f...

Page 117: ...Overvoltage Arresters C f Figure 10 2 Lightning arrester C f C in F 4 85x10 11 4 80x10 11 4 75x10 11 4 70x10 11 4 65x10 11 4 60x10 11 4 55x10 11 4 50x10 11 4 45x10 11 4 40x10 11 4 35x10 11 4 30x10 11...

Page 118: ...CP TD1 Reference Manual V 1 44 118 Rp f Figure 10 3 Lightning arrester Rp f Rp in 14 0x108 12 0x108 10 0x105 8 0x108 6 0x108 4 0x108 2 0x108 0 0 0 0Hz 100Hz 200Hz 300Hz 400Hz f in Hz...

Page 119: ...0 15 400Hz Terminal U f THD I S tmax High volt output 10 12kV AC 15 400Hz 2 300mA 3600VA 2min 100mA 1200VA 60min Range Resolution Typical accuracy 15 400Hz 0 01Hz error 0 005 of reading 50Hz 60Hz Meas...

Page 120: ...of reading Ix 8mA Range Resolution Typical accuracy 0 12000V AC 1V error 0 3 of reading 1V Range Resolution Typical accuracy Conditions 1pF 3 F 6 digits error 0 05 of reading 0 1pF Ix 8mA Vtest 300V...

Page 121: ...umn f 45 70Hz I 8mA Vtest 300V 10kV 0 100 5 digits error 0 5 of reading 0 02 Vtest 300V 10kV Range Resolution Typ accuracy Conditions 90 90 4 digits error 0 01 Vtest 300V 10kV Range Resolution Typ acc...

Page 122: ...450 x 330 x 220mm 17 7 x 13 x 8 7 without handles test set case1 21kg 46 3lbs 700 x 500 x 420mm 27 5 x 19 7 x 16 5 Cables and accessories equipment 16 6kg 36 6lbs equipment case1 26 6kg 58 7lbs 680 x...

Page 123: ...g to IEC 60068 2 78 Table 11 2 Shock Vibration Noise Immunity Characteristic Rating Shock IEC 60068 2 27 operating 15 g 11 ms half sinusoid Vibration IEC 60068 2 6 operating 10 to 150 Hz acceleration...

Page 124: ...Council of the European Community for meeting the requirements of the member states regarding the electromagnetic compatibility EMC Directive 2004 108 EC and the low voltage Directive 2006 95 EC EMC E...

Page 125: ...ial 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 CP TD1 2 Different high voltage clamps 2 Low voltage clamp...

Page 126: ...es were measured enter them into the respective entry fields of the TanDelta test card s Settings Page at Compensations refer to 3 4 on page 30 Characteristic Rating Temperature Range 10 60 C 14 140 F...

Page 127: ...le length 1 m Equipment description Article number CP TD1 TanDelta test set including software TanDelta test card accessories and trolley CPC 100 test system VE000640 CP TD1 TanDelta test set includin...

Page 128: ...CP TD1 Reference Manual V 1 44 128...

Page 129: ...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 F...

Page 130: ...D1 Reference Manual V 1 44 130 12 2 Negative DF Measurements Surface current R C11 C12 C13 C1n 1 C1n C2 C1a 1 1 C11 1 C12 1 C13 Zi 0 Measuring tap C1 U2 U1 1 1 1 R j C1n j C1a U1 C1a C1n R U2 IC1n Bus...

Page 131: ...131 Appendix U2 U1 1 1 C1n C1a j 1 R C1a U2 U1 1 C1n C1a j 1 R C1a 1 C1n C1a 2 1 R C1a 2 arc 1 R C1a 1 C1n C1a tan jImaginary IC1n Re U2 U1 This angle will be measured with TD1 negative tan...

Page 132: ...ground High and tertiary to low and ground Note 1 While the real significance that can be attached to the power factor of liquid immersed transformers is still a matter of opinion experience has show...

Page 133: ...ngs With kind permission of Pritpal Singh ABB Inc USA 12 5 1 Abstract Measurement of C2 power factor and capacitance of condenser bushings has been a topic of much interest among the utility and other...

Page 134: ...nce between bushings of different voltage classes designs and discusses the factors that can influence these measurements 12 5 3 Design Construction of C1 and C2 Capacitance in Condenser Bushings As p...

Page 135: ...ed during the condenser winding process The C1 layer foil is internally connected to the test tap These bushings have an inherent C2 capacitance which is formed by the insulation between the C1 layer...

Page 136: ...ontrolled by design and are mainly dependent upon oil impregnated paper insulation Therefore the power factor and capacitance test values under normal circumstances are not affected too much by extern...

Page 137: ...wet resistance between bushing mounting flange and the transformer tank stray effect from other objects and external connections during testing These bushings have an inherent C2 capacitance which is...

Page 138: ...rnal C1 layer foil and a short mounting flange is the external ground plane The following table shows the effect of proximity and type of ground plane on power factor and capacitance of two different...

Page 139: ...sed in oil the increase in capacitance would be higher as the oil has a higher dielectric constant Another observable fact is the small difference of C2 PF and CAP test values of Type T bushing betwee...

Page 140: ...ing mounted on a metallic test tank stand with the lower end porcelain immersed in dry good quality oil There should be sufficient clearance at least 16 20 inch from the bushing lower porcelain termin...

Page 141: ...TN and now with ABB Inc Alamo TN He has been an active member of the IEEE Transformer Committee for the past 20 years and was the Chair of the WG for the revision of IEEE Std C57 19 01 2000 Presently...

Page 142: ...imits of the dissipation factor at 20 C b Limits of the capacitance change Delta C at 20 C Source Widmann Karl Zustandserfassung und Bewertung von Durchf hrungen im Betrieb MICAFIL Symposium Stuttgart...

Page 143: ...ic A 6 0 8 0 B 10 0 12 0 F 1 5 2 0 L 3 4 0 LC 2 5 3 5 OF 2 6 6 0 S 3 5 6 0 U 1 0 1 5 Lapp bushings POC 0 5 PRC 0 7 1 2 Ohio Brass manufactured prior to 1926 and after 1938 ODOF G L 1 10 Initial P F 22...

Page 144: ...800kV GOA 250 GOB GOBK GOC GOE GOE GOEK GOEL GOF GOFL GOG GOH GOM GOA other 0 5 0 5 0 5 0 4 0 45 0 4 0 4 0 4 0 45 0 4 0 45 0 25 0 45 0 45 0 7 0 7 0 7 0 6 0 65 0 6 0 6 0 6 0 65 0 6 0 65 0 45 0 65 0 65...

Page 145: ...A COTA 0 3 0 35 Double Name plate Note 1 C1 capacitance is doubtful if 10 over nameplate 2 C1 capacitance is doubtful if 5 over first measurement in field after installation 3 C2 capacitance may vary...

Page 146: ...nce measurement dynamic tap changer testing ratio leakage reactance capacitance and dissipation factor measurement By Michael Kr ger OMICRON electronics GmbH Austria Lapp Paper Oil Condenser type Tota...

Page 147: ...any With the advancing age of transformers a regular check of the operating conditions becomes more and more important The Dissolved Gas Analysis is a proven and meaningful method such that if increas...

Page 148: ...8 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...

Page 149: ...r However there are many other possible reasons for increased gas values in the oil An example might be decomposed oil leaking from the diverter switch into the transformer oil through a defective sea...

Page 150: ...ement of leakage reactance Capacitance and Dissipation factor measurement Figure 12 8 A multi functional transformer test and diagnosis system In this paper all tests were performed with a new self co...

Page 151: ...t Winding resistances are tested in the field to check for loose connections broken strands and high contact resistance in tap changers Additionally the dynamic resistance measurement enables an analy...

Page 152: ...xt while carrying load current The commutation resistances R limit the short circuit current between the taps which could otherwise become very high due to the interruption free switching of the conta...

Page 153: ...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...

Page 154: ...CP TD1 Reference Manual V 1 44 154 Figure 12 12 Diverter switch for 110 kV 40 MVA...

Page 155: ...rated current to bring the core into saturation On the other hand it should not exceed 15 of the rated current to avoid temperature rise during measurement A relatively high no load voltage enables a...

Page 156: ...9 6 Safety Aspects Feeding currents of several amps through a coil rated at hundreds of Henries causes a high magnetic energy to be stored in the coil inductance If the measuring circuit was interrupt...

Page 157: ...y but calculated from the measured Ra Rb and Rc values Ra R1 R2 Rb R2 R3 Rc R3 R1 Y connection without Neutral Rc Rb Ra 2 R1 R1 Rc Ra Rb 2 Ra Rc Rb 2 R2 R2 Ra Rb Rc 2 Rb Ra Rc 2 R3 R3 Rb Rc Ra 2 Close...

Page 158: ...he values measured by the manufacturer for the mid position denoted as tap 10 of the tap selector in all phases where direct connection to the main winding occurs Figure 12 16 Winding resistance measu...

Page 159: ...sistances 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 Fi...

Page 160: ...Resistance after maintenance To examine the results in more detail it is recommended to graph the difference between UP and DOWN values Figure 12 19 The difference before contact maintenance was up to...

Page 161: ...dix 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 Differenc...

Page 162: ...t the test current should be as low as possible otherwise short interruptions or bouncing of the diverter switch contacts cannot be detected In this case the initiated arc has the effect of shortening...

Page 163: ...elay operation The turns ratio test detects shorted turns which indicate insulation failure Shorted turns may result from short circuits with high currents or insulation failures The voltage ratio obt...

Page 164: ...nce Manual V 1 44 164 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 pha...

Page 165: ...e For intact windings this ratio is nearly totally independent from the frequency in the discussed frequency range The ratio was measured with a test voltage of 200 V on the HV side The excitation cur...

Page 166: ...considered 12 9 12 Leakage Reactance The measurement of the short circuit impedance is done as part of the initial acceptance test in the factory The leakage reactance can be calculated from the shor...

Page 167: ...ctural problems displaced wedging buckling etc This test does not replace excitation current tests or capacitance tests but complements them and they are often used together The excitation current tes...

Page 168: ...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 In this case th...

Page 169: ...ablished 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 Cp represents the cap...

Page 170: ...ce Manual V 1 44 170 The vector diagram of the system is shown in Figure 12 27 Figure 12 27 Definition of dissipation factor tan and the vector diagram Re IRp U ICp I jIm tan IRp ICP 1 1 Cp with 2 f a...

Page 171: ...delta was the mentioned Schering bridge 9 Figure 12 28 Figure 12 28 Schering bridge Real parts Imaginary parts C1 C2 R1 R3 R4 C4 R1 1 j C1 R3 1 R4 j C4 j C2 R1 R3 C4 C2 R1 C4 C2 R3 C1 R3 C2 R4 C1 R4...

Page 172: ...n Figure 12 29 doesn t require tuning for measuring C and DF Cn is a gas insulated reference capacitor with losses below 10E 5 Figure 12 29 CP TD1 measuring principle For laboratory use such capacitor...

Page 173: ...power factor was measured only at line frequency With the power source described in 8 it is now possible to make these insulation measurements in a wide frequency range Beside the possibility to appl...

Page 174: ...sformer C Tan Delta measurements are made for all insulation gaps HV to LV HV to ground LV to ground Figure 12 31 A three winding transformer is much more complicated and more tests are necessary to m...

Page 175: ...by lightning strikes or through faults can cause a change of the measured capacitance values This indicates winding deformation and structural problems such as displaced wedging and winding support 12...

Page 176: ...pes of bushings Resin impregnated paper RIP Oil impregnated paper OIP and Resin bonded paper RBP Figure 12 33 Aging of RBP RIP and OIP bushings change of capacitance 10 10 8 6 4 2 0 10 8 6 4 2 0 10 8...

Page 177: ...e 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...

Page 178: ...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 H...

Page 179: ...ple electrical methods such as resistance measurements The described new test technology enables DF frequency scans which by comparing DF curves to fingerprints it will be possible to detect degradati...

Page 180: ...g und berwachung von Transformatoren durch Analyse der im l gel sten Gase Sonderdruck aus Elektrizit tswirtschaft Trafo Union N rnberg 1981 TU 81 5 19 1 75 6 Foschum H Erfahrungsbericht zur Gasanalyse...

Page 181: ...Page 2 2 on page 30 where PF DF 20 is the corrected Power Factor Dissipation Factor to 20 C PF DF T is the Power Factor Dissipation Factor measured at T k is the correction factor 12 11 1 Transformer...

Page 182: ...e determined by long time studies of a utility 0 10 20 30 40 50 60 70 80 90 100 Temperature in C 1 1 1 0 0 9 0 8 0 7 0 6 DF Correction Factor k Resin Impregnated Paper RIP 0 10 20 30 40 50 60 70 80 90...

Page 183: ...183 Appendix 0 10 20 30 40 50 60 70 80 90 100 Temperature in C 1 1 1 0 0 9 0 8 DF Correction Factor k Oil Impregnated Paper OIP...

Page 184: ...CP TD1 Reference Manual V 1 44 184...

Page 185: ...006 20 F Tower 2 The Gateway Harbour City Kowloon Hong Kong S A R Phone 852 3767 5500 Fax 852 3767 5400 support asia omicron at www omicron at Europe Middle East Africa OMICRON electronics GmbH Oberes...

Page 186: ...CP TD1 Reference Manual V 1 44 186...

Page 187: ...T measuring modes CP TD1 TanDelta 27 H high voltage plug at CP TD1 11 hotline 185 I IEC 68 2 78 123 M maintenance 9 measuring modes UST GST CP TD1 TanDelta 27 O ordering information calibration set CP...

Page 188: ...185 temperature temp measuring unit TH 3631 126 test grounding set for test object 23 36 preparation of substation 23 36 test card TanDelta 25 test object preparation prior to test 23 36 TH 3631 opti...

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