[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

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a reliable and cost-effective transformer insulation structure. The power engineer models not only the transformer, but also the system in order to investigate the effects of power-system transients. Considerable effort has been devoted to computing the transformer’s internal transient response. Models of this type may contain several hundred nodes for each phase. This detail is necessary in order to compute the internal response in enough detail to establish an adequate transformer insulation design. The utility engineer usually is not interested in the internal response, but is concerned only with the transformer’s terminal response. Even if the transformer’s detailed model were available, its use would create system models too large to be effectively used in system studies. What has been the normal practice is to create a reduced-order model of the transformer that represents the terminal response of the transformer. Experience has shown that great care must be taken to obtain a terminal model that provides a reasonable representation of the transformer over the frequency range of interest [24,27]. The challenge in creating a high-fidelity reduced model lies in the fact that as the size of the model is reduced, the number of valid eigenvalues must also decrease. In effect, any static reduction technique will produce a model that is intrinsically less accurate than the more detailed lumped-parameter model [54,55]. 3.10.9.2 Reduced-Order Model McNutt et al. [31] suggested a method of obtaining a reduced-order transformer model by starting with the detailed model and appropriately combining series and shunt capacitances. This suggestion was extended by de Leon [55]. This method is limited to linear models and can not be used to eliminate large proportions of the detailed models without effecting the resulting model accuracy. Degeneff [38] proposed a terminal model developed from information from the transformer’s name plate and capacitance as measured among the terminals. This model is useful below the first resonant frequency, but it lacks the necessary accuracy at higher frequencies for system studies. Dommel et al. [56] proposed a reduced model for EMTP described by branch impedance or admittance matrix calculated from openand short-circuit tests. TRELEG and BCTRAN matrix models for EMTP can be applied only for verylow-frequency studies. Morched et al. [54] proposed a terminal transformer model, composed of a synthesized LRC network, where the nodal admittance matrix approximates the nodal admittance matrix of the actual transformer over the frequency range of interest. This method is appropriate only for linear models. Other references [24,25] present a method for reducing both a detailed linear and nonlinear lumpedparameter model to a terminal model with no loss of accuracy. The work starts with equation 1, progresses to equation 4, and then applies Kron reduction to obtain a terminal model of the transformer that retains all the frequency fidelity of the initial transformer lumped-parameter model. All of the appropriate equations to apply this technique within EMTP are available in the literature [24,25]. References 1. Blume, L.F., Boyajian, A., Camilli, G., Lennox, T.C., Minneci, S., and Montsinger, V.M., Transformer Engineering, 2nd ed., John Wiley and Sons, New York, 1954, pp. 416–423. 2. Bean, R.L., Crackan, N., Moore, H.R., and Wentz, E., Transformers for the Electric Power Industry, McGraw-Hill, New York, 1959. Reprint, Westinghouse Electric Corp., New York, 1959. 3. Massachusetts Institute of Technology, Department of Electrical Engineering: Magnetic Circuits and Transformers, John Wiley and Sons, New York, 1943. 4. Franklin, A.C., The J & P Transformer Book, 11th ed., Butterworth, London, 1983, chap. 15, pp. 351–367. 5. Kogan, V.I., Fleeman, J.A., Provanzana, J.H., and Shih, C.H., Failure analysis of EHV transformers, IEEE Trans. Power Delivery, PAS-107, 672–683, 1988. 6. An international survey on failures in large power transformers in service, final report of Working Group 05 of Study Committee 12 (Transformers), Electra, 88, 49–90, 1983. 7. Kogan, V.I., Fleeman, J.A., Provanzana, J.H., Yanucci, D.A., and Kennedy, W.N., Rationale and Implementation of a New 765-kV Generator Step-Up Transformer Specification, CIGRE Paper 12- 202, Cigre, Paris, August 1990. 8. IEEE, Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems, IEEE Std. 519, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1999. 9. Degeneff, R.C., Neugebaur, W., Panek, J., McCallum, M.E., and Honey, C.C., Transformer response to system switching voltages, IEEE Trans. Power Appar. Syst., 101, 1457–1465, 1982. 10. Greenwood, A., Vacuum Switchgear, Institute of Electrical Engineers, Short Run Press, Exeter, U.K., 1994. 11. Narang, A., Wisenden, D., and Boland, M., Characteristics of Stress on Transformer Insulation Subjected to Very Fast Transient Voltages, CEA No. 253 T 784, Canadian Electricity Association, Hull, Quebec, Canada, July 1998. 12. Abetti, P.A., Survey and classification of published data on the surge performance of transformers and rotating machines, AIEE Trans., 78, 1403–1414, 1959. 13. Abetti, P.A., Survey and classification of published data on the surge performance of transformers and rotating machines, 1st supplement, AIEE Trans., 81, 213, 1962. 14. Abetti, P.A., Survey and classification of published data on the surge performance of transformers and rotating machines, 2nd supplement, AIEE Trans., 83, 855, 1964. 15. Abetti, P.A., Pseudo-final voltage distribution in impulsed coils and windings, AIEE Trans., 87–91, 1960. 16. Waldvogel, P. and Rouxel, R., A new method of calculating the electric stresses in a winding subjected to a surge voltage, Brown Boveri Rev., 43, 206–213, 1956. 17. McWhirter, J.H., Fahrnkopf, C.D., and Steele, J.H., Determination of impulse stresses within transformer windings by computers, AIEE Trans., 75, 1267–1273, 1956. 18. Dent, B.M., Hartill, E.R., and Miles, J.G., A method of analysis of transformer impulse voltage distribution using a digital computer, IEEE Proc., 105, 445–459, 1958. 19. White, W.N., An Examination of Core Steel Eddy Current Reaction Effect on Transformer Transient Oscillatory Phenomena, GE Technical Information Series, No. 77PTD012, General Electric Corp., Pittsfield, MA, April 1977. 20. Degeneff, R.C., Blalock, T.J., and Weissbrod, C.C., Transient Voltage Calculations in Transformer Winding, GE Technical Information Series, No. 80PTD006, General Electric Corp., Pittsfield, MA, 1980. 21. White, W.N., Numerical Transient Voltage Analysis of Transformers and LRC Networks Containing Nonlinear Resistive Elements, presented at 1977 PICA Conference, Toronto, pp. 288–294. 22. Wilcox, D.J., Hurley, W.G., McHale, T.P., and Conton, M., Application of modified modal theory in the modeling of practical transformers, IEEE Proc., 139, 472–481, 1992. 23. Vakilian, M., A Nonlinear Lumped Parameter Model for Transient Studies of Single Phase Core Form Transformers, Ph.D. thesis, Rensselaer Polytechnic Institute, Troy, New York, August 1993. 24. Gutierrez, M., Degeneff, R.C., McKenny, P.J., and Schneider, J.M., Linear, Lumped Parameter Transformer Model Reduction Technique, IEEE Paper No. 93 SM 394-7 PWRD, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1993. 25. Degeneff, R.C., Gutierrez, M., and Vakilian, M., Nonlinear, Lumped Parameter Transformer Model Reduction Technique, IEEE Paper No. 94 SM 409-3 PWRD, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1994. 26. de Leon, F. and Semlyen, A., Complete transformer model for electromagnetic transients, IEEE Trans. Power Delivery, 9, 231–239, 1994. 27. Degeneff, R.C., A general method for determining resonances in transformer windings, IEEE Trans. Power Appar. Syst., 96, 423–430, 1977. 28. Dommel, H.W., Digital computer solution of electromagnetic transients in single and multiphase networks, IEEE Trans. Power Appar. Syst., PAS-88, 388–399, 1969. © 2004 by CRC Press LLC © 2004 by CRC Press LLC
29. Degeneff, R.C., Reducing Storage and Saving Computational Time with a Generalization of the Dommel (BPA) Solution Method, presented at IEEE PICA Conference, Toronto, 1977, pp. 307–313. 30. FORTRAN Subroutines for Mathematical Applications, Version 2.0, MALB-USM-PERFCT- EN9109-2.0, IMSL, Houston, TX, September 1991. 31. McNutt, W.J., Blalock, T.J., and Hinton, R.A., Response of transformer windings to system transient voltages, IEEE Trans. Power Appar. Syst., 93, 457–467, 1974. 32. Abetti, P.A., Correlation of forced and free oscillations of coils and windings, IEEE Trans. Power Appar. Syst., 78, 986–996, 1959. 33. Abetti, P.A. and Maginniss, F.J., Fundamental oscillations of coils and windings, IEEE Trans. Power Appar. Syst., 73, 1–10, 1954. 34. Grover, F.W., Inductance Calculations — Working Formulas and Tables, Dover Publications, New York, 1962. 35. Rabins, L., Transformer reactance calculations with digital computers, AIEE Trans., 75, 261–267, 1956. 36. Fergestad, P.I. and Henriksen, T., Transient oscillations in multiwinding transformers, IEEE Trans. Power Appar. Syst., 93, 500–507, 1974. 37. White, W.N., Inductance Models of Power Transformers, GE Technical Information Series, No. 78PTD003, General Electric Corp., Pittsfield, MA, April 1978. 38. Degeneff, R.C., A Method for Constructing Terminal Models for Single-Phase n-Winding Transformers, IEEE Paper A78 539-9, Summer Power Meeting, Los Angeles, 1978. 39. Degeneff, R.C. and Kennedy, W.N., Calculation of Initial, Pseudo-Final, and Final Voltage Distributions in Coils Using Matrix Techniques, Paper A75-416-8, presented at Summer Power Meeting, San Francisco, 1975. 40. Snow, C., Formulas for Computing Capacitance and Inductance, NBS Circular 544, National Institutes of Standards and Technology, Gaithersburg, MD, 1954. 41. Clark, F.M., Insulating Materials for Design and Engineering Practice, Wiley, New York, 1962. 42. von Hippel, A., Dielectric Materials and Applications, Massachusetts Institute of Technology, Cambridge, 1954. 43. Fink, D.G. and Beaty, H.W., Standard Handbook for Electrical Engineers, 12th ed., McGraw-Hill, New York, 1987. 44. Scheich, A., Behavior of Partially Interleave Transformer Windings Subject to Impulse Voltages, Bulletin Oerlikon, No. 389/390, Oerlikon Engineering Co., Zurich, 1960, pp. 41–52. 45. Degeneff, R.C., Simplified Formulas to Calculate Equivalent Series Capacitances for Groups of Disk Winding Sections, GE TIS 75PTD017, General Electric Corp., Pittsfield, MA, 1976. 46. Greenwood, A., Electrical Transients in Power Systems, John Wiley & Sons, New York, 1991. 47. Lammeraner, J. and Stafl, M., Eddy Currents, Chemical Rubber Co. Press, Cleveland, 1966. 48. Tarasiewicz, E.J., Morched, A.S., Narang, A., and Dick, E.P., Frequency dependent eddy current models for the nonlinear iron cores, IEEE Trans. Power Appar. Syst., 8, 588–597, 1993. 49. Avila-Rosales, J. and Alvarado, F.L., Nonlinear frequency dependent transformer model for electromagnetic transient studies in power systems, IEEE Trans. Power Appar. Syst., 101, 4281–4289, 1982. 50. Batruni, R., Degeneff, R., and Lebow, M., Determining the effect of thermal loading on the remaining useful life of a power transformer from its impedance versus frequency characteristic, IEEE Trans. Power Delivery, 11, 1385–1390, 1996. 51. IEEE, Guide and Standards for Distribution, Power, and Regulating Transformers, C57-1990, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1990. 52. Balma, P.M., Degeneff, R.C., Moore, H.R., and Wagenaar, L.B., The Effects of Long-Term Operation and System Conditions on the Dielectric Capability and Insulation Coordination of Large Power Transformers, Paper No. 96 SM 406-9 PWRD, presented at the summer meetings of IEEE/PES, Denver, CO, 2000. 53. IEEE, Guide for the Application of Metal-Oxide Surge Arrester for Alternating-Current Systems, C62.22-1991, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1991. 54. Morched, A., Marti, L., and Ottevangers, J., A High Frequency Transformer Model for EMTP, No. 925M 359-0, presented at IEEE 1992 Summer Meeting, Seattle, WA. 55. de Leon, F. and Semlyen, A., Reduced order model for transformer transients, IEEE Trans. Power Delivery, 7, 361–369, 1992. 56. Dommel, H.W., Dommel, I.I., and Brandwajn, V., Matrix representation of three-phase n-winding transformers for steady state and transient studies, IEEE Trans. Power Appar. Syst., PAS-101, 1982. 3.11 Transformer Installation and Maintenance Alan Oswalt 3.11.1 Transformer Installation The first priority is to hire a reliable contractor to move and assemble the transformer. There are many stories where the contractors, lacking experience or proper equipment, drop the transformer or do not assemble the components correctly. Accepting a low bid could cost your company more than securing a competent contractor. Do not assume that all manufacturers have the same methods of installation. Your understanding of the manufacturer’s transformer installation book and reviewing the complete set of drawings in advance will help you to understand “their” procedures. Some manufacturers have a toll-free number which allows you to clarify drawings and/or the assembly methods. Others have put together a series of videos and/ or CDs that will assist you to understand the complete assembly. Then you should review all of the information with your assembly contractor. 3.11.1.1 Receiving Inspection Prior to unloading a transformer and the accessories, a complete inspection is necessary. If any damage or problems are found, contact the transformer manufacturer before unloading. Freight damage should be resolved, as it may be required to return the damaged transformer or the damaged accessories. Photographs of the damage should be sent to the manufacturer. Good receiving records and photographs are important, should there be any legal problems. Three important inspections checks are (1) loss of pressure on the transformer, (2) above zone 3 on the impact recorder, and (3) signs of movement by the transformer or its accessories. If any of the three inspection checks indicate a problem, an internal inspection is recommended. A shorted core reading could also mean a bad transit ride. With a railroad shipment, if any of the checks indicate problems and an internal inspection does not reveal the problem, get an exception report filled out by a railroad representative. This report will assist you later if hidden damages are found. Low core meggar readings (200 Megohms) could be an indication of moisture in the unit and require extra costs to remove. 2 The moisture could have entered the unit through a cracked weld caused by the bad transit ride. (See Figs. 3.11.1 and 3.11.2.) Entering a unit requires good confined entry procedures and can be done after contacting the manufacture, as they may want to have a representative present to do the inspection. Units shipped full of oil require a storage tanker and the costs should be agreed upon before starting. Assuming that we now have a good transformer and it is setting on its substation pad, there are some items that are essential for assembly. First ground the transformer before starting the assembly. Static 2 A dew point test will determine the moisture in the transformer. A dew point reading should be used with the winding temperature value (insulation temperature) to determine the percentage of moisture. (See Figs. 3.11.1 and 3.11.2.) © 2004 by CRC Press LLC © 2004 by CRC Press LLC
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ELECTRIC POWER TRANSFORMER ENGINEER
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I wish to recognize the interest of
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Contents 1 Theory and Principles Ch
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1.3 Equivalent Circuit of an Iron-C
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designer starts to make a design fo
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• Transient voltages generated du
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the transformer’s bushings and, m
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% regulation = [(V NL - V FL )/V FL
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In core-form transformers, the wind
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FIGURE 2.1.14 Layer windings (singl
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the transformer design, which may b
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consumer’s service circuit is a d
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FIGURE 2.2.3 Single-phase transform
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is installed so that the tank never
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above which persons might be burned
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FIGURE 2.2.16 Two-bushing subway. (
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carbon steel or the very expensive
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FIGURE 2.2.31 Radial-style dead fro
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FIGURE 2.2.36 Complete transformer
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voltage in each winding simultaneou
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mounted transformers can have arres
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V S + V S I V L Z=R+jX a) V L V S V
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Z = jX (2.3.19) 0.7 Then the curren
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X1 L* X1 S =X1 L X2 L* X3 L* a) S L
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150 V(%) 100 50 0 -50 40 80 T(s) 12
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2.3.8.1.2 Series Connection • The
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A six-pulse single-way transformer
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The degree of coupling also influen
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where I h = current for the hth har
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In the case of liquid-filled transf
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FIGURE 2.4.21 A 36-pulse system mad
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Vacuum-pressure encaps ulated — T
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FIGURE 2.6.1 Typical wiring and sin
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a) H1 b) Ip X2 FLUX H2 LEAKAGE FLUX
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and for CTs is TCF = RCF - (PA/2600
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RCF x Bx Bt RCF t - RCF 0 co
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2000 1000 5% Vex BANDWITH FROM NOMI
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This may be more useful when operat
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also some uncertainty in repeatabil
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FIGURE 2.6.25 Standard two-element
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2.7 Step-Voltage Regulators Craig A
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Source Bypass Switch Source Bypass
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2.7.4 Theory A step-voltage regulat
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FIGURE 2.7.22 Equalizer winding inc
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TABLE 2.7.4 Increase in Ampere Load
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References IEEE, Standard Requireme
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300% FIGURE 2.8.4 Schematic of a co
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TABLE 2.8.1 Typical Sizing Workshee
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Input with Interruption Ferro Outpu
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FIGURE 2.8.20A Performance of a rid
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• Input frequency or frequency ra
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References 1. Sola/Hevi-Duty Corp.,
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FIGURE 2.9.5 Typical phase-reactor
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FIGURE 2.9.10 Two generator arrange
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• Overloading of lines • Increa
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FIGURE 2.9.23 34-kV, 25-MVAR (per p
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V 90 ( X X ) s T (2.9.10a) where,
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Therefore, Line reactive losses = (
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ate of rise of transient-recovery v
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the LLCR is provided in IEEE Std. C
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aluminum shielding, i.e., an oil-im
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Leo J. Savio ADAPT Corporation Ted
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3.1.2.2.2 Heat Dissipation A second
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FIGURE 3.2.1 Solid-type bushing. ma
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1.6 cm. This means that most of the
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where HS = steady-state bushing ho
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the conductivity of the water-solub
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of 178 ohm-m, and a test duration o
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2. Easley, J.K. and Stockum, F.R.,
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FIGURE 3.3.5 Reactance-type LTC, in
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FIGURE 3.3.10 LTC with delta connec
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3.3.5 Selection of Load Tap Changer
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FIGURE 3.3.19 Effect of the leakage
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References Goosen, P.V. , Transform
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If i 1 is the full-load current rat
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TABLE 3.4.1 Loading Recommendations
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3.5.4 Three-Phase Transformer Conne
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FIGURE 3.5.4 Interconnected star-gr
Page 157 and 158: 3.6.1.1 Standards ANSI standards fo
Page 159 and 160: ANSI standards. LTC control setting
Page 161 and 162: FIGURE 3.6.7 Discharging the capaci
Page 163 and 164: FIGURE 3.6.10 Standard switching-im
Page 165 and 166: voltage of the excited winding, rea
Page 167 and 168: FIGURE 3.6.18 Current, voltage, and
Page 169 and 170: TABLE 3.6.3 Transformer Short-Circu
Page 171 and 172: FIGURE 3.7.3 Control for voltage re
Page 173 and 174: FIGURE 3.7.6A Feeder with power-fac
Page 175 and 176: 3. Circulating current (current bal
Page 177 and 178: FIGURE 3.7.10 Control block diagram
Page 179 and 180: Primary Current (Amps) 60 40 20 0 -
Page 181 and 182: current transformer having two prim
Page 183 and 184: 87R1 87BL1 (A) Independent Harmonic
Page 185 and 186: Winding 1 Secondary Currents Data A
Page 187 and 188: Y Y 20 18 3 rd Harmonic CTR1=40 CTR
Page 189 and 190: 230 kV 3 180 MVA 138 kV 5 CTR1 = 2
Page 191 and 192: 29. Concordia, C. and Rothe, F.S.,
Page 193 and 194: FIGURE 3.9.1 Measurement of pressur
Page 195 and 196: H 2m 1. Vertical Forced Air 2. Prin
Page 197 and 198: Gade, S., Sound Intensity Instrumen
Page 199 and 200: nected. This steady-state voltage d
Page 201 and 202: where [A] = state matrix [B] = inpu
Page 203 and 204: where C = capacitance between the t
Page 205 and 206: L ijo = N i N j ijo (3.10.31) 1.4
Page 207: % VOLTAGE % VOLTAGE 100 BIL 90 50 3
Page 211 and 212: All connections should be cleaned a
Page 213 and 214: 6. Costs to set up and use a mobile
Page 215 and 216: Records of relay operation must be
Page 217 and 218: • Has heating occurred as the res
Page 219 and 220: a reference value) of the currents
Page 221 and 222: The next data-processing step is to
Page 223 and 224: temperature. As the transformer coo
Page 225 and 226: 3.13.3.2 Instrument Transformers Th
Page 227 and 228: FIGURE 3.13.5 Analysis of bushing s
Page 229 and 230: temperature. Under abnormal conditi
Page 231 and 232: 3.14.1.2 Accredited Standards Commi
Page 233 and 234: FIGURE 3.14.4 IEC technical-committ
Page 235 and 236: TABLE 3.14.2 Relevant Documents for
Page 241: TABLE 3.14.13 Relevant Documents fo
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