[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

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FIGURE 3.8.30 DC content of the differential current for Case 3. TABLE 3.8.3 Inrush Detection Methods Performance during Inrush Conditions Method Case 1 Case 2 Case 3 Low even-harmonic Second-harmonic setting content 6% 8% Second- and fourthharmonic blocking All-harmonic restraint Low-current detection Even-harmonic restraint DC-ratio blocking 4. An improved approach for transformer protection that combines harmonic-restraint and -blocking methods with a waveshape-recognition technique provides added security to the independent harmonic-restraint element without sacrificing dependability. This new method uses even harmonics for restraint, plus dc component and fifth harmonic for blocking. 5. Using even-harmonic restraint ensures security for inrush currents with low second-harmonic content and maintains dependability for internal faults with CT saturation. The use of fifthharmonic blocking guarantees an invariant relay response to overexcitation. Using dc-offset blocking ensures security for inrush conditions with very low total harmonic distortion. References Percentage 100 90 80 70 60 50 40 0 1 2 3 4 5 6 7 Cycles High third-harmonic content Low-current interval = 1 / 4 cycle Low even-harmonic content DC ratio = zero Note: = Correct operation; = Misoperation. Even-harmonic content Low-current interval > 1 / 4 cycle Even-harmonic content DC ratio > 0.1 after 1 cycle Second-harmonic setting Harmonic content Low-current interval < 1 / 4 cycle Even-harmonic content DC ratio = zero 1. Klingshirn, E.A., Moore, H.R., and Wentz, E.C., Detection of faults in power transformers, AIEE Trans., 76, 87–95, 1957. 2. Madill, J.T., Typical transformer faults and gas detector relay protection, AIEE Trans., 66, 1052–1060, 1947. 3. Bean, R.L. and Cole, H.L., A sudden gas pressure relay for transformer protection, AIEE Trans., 72, 480–483, 1953. 4. Monseth, I.T. and Robinson, P.H., Relay Systems: Theory and Applications, McGraw Hill, New York, 1935. 5. Sleeper, H.P., Ratio differential relay protection, Electrical World, 827831, October 1927. 6. Cordray, R.E., Percentage differential transformer protection, Electrical Eng., 50, 361–363, 1931. 7. Cordray, R.E., Preventing false operation of differential relays, Electrical World, 160–161, July 25, 1931. 8. Harder, E.L. and Marter, W.E., Principles and practices of relaying in the United States, AIEE Trans., 67, 1005–1023, 1948. 9. Kennedy, L.F., and Hayward, C.D., Harmonic-current-restrained relays for differential protection, AIEE Trans., 57, 262–266, 1938. 10. Hayward, C.D., Harmonic-current-restrained relays for transformer differential protection, AIEE Trans., 60, 377–382, 1941. 11. Mathews, C.A., An improved transformer differential relay, AIEE Trans., 73, 645–650, 1954. 12. Sharp, R.L. and Glassburn, W.E., A transformer differential relay with second-harmonic restraint, AIEE Trans., 77, 913–918, 1958. 13. Einval, C.H. and Linders, J.R., A three-phase differential relay for transformer protection, IEEE Trans., PAS-94, 1971–1980, 1975. 14. Dmitrenko, A.M., Semiconductor pulse-duration differential restraint relay, Izv. Vysshikh Uchebnykh Zavedenii, Elektromekhanika, No. 3, 335–339, March 1970 (in Russian). 15. Atabekov, G.I., The Relay Protection of High Voltage Networks, Pergamon Press, London, 1960. 16. Rockefeller, G.D., Fault protection with a digital computer, IEEE Trans., PAS-98, 438464, 1969. 17. Wilkinson, S.B., Transformer Differential Relay, U.S. Patent 5,627,712, May 6, 1997. 18. Hayward, C.D., Prolonged inrush currents with parallel transformers affect differential relaying, AIEE Trans., 60, 10961101, 1941. 19. Blume, L.F., Camilli, G., Farnham, S.B., and Peterson, H.A., Transformer magnetizing inrush currents and influence on system operation, AIEE Trans., 63, 366375, 1944. 20. Specht, T.R., Transformer magnetizing inrush current, AIEE Trans., 70, 323328, 1951. 21. AIEE Committee Report, Report on transformer magnetizing current and its effect on relaying and air switch operation, AIEE Trans., 70, 17331740, 1951. 22. Sonnemann, W.K., Wagner, C.L., and Rockefeller, G.D., Magnetizing inrush phenomena in transformer banks, AIEE Trans., 77, 884892, 1958. 23. Berdy, J., Kaufman, W., and Winick, K., A Dissertation on Power Transformer Excitation and Inrush Characteristics, presented at Symposium on Transformer Excitation and Inrush Characteristics and Their Relationship to Transformer Protective Relaying, Houston, TX, 1976. 24. Zocholl, S.E., Guzmán, A., and Hou, D., Transformer Modeling as Applied to Differential Protection, presented at 22nd Annual Western Protective Relay Conference, Spokane, WA, 1995. 25. Cooper Power Systems, Electric Power System Harmonics: Design Guide, Cooper Power Systems, Bulletin 87011, Franksville, WI, 1990. 26. Waldron, J.E. and Zocholl, S.E., Design Considerations for a New Solid-State Transformer Differential Relay with Harmonic Restraint, presented at Fifth Annual Western Protective Relay Conference, Sacramento, CA, 1978. 27. Marshall, D.E. and Langguth, P.O., Current transformer excitation under transient conditions, AIEE Trans., 48, 14641474, 1929. 28. Wentz, E.C. and Sonnemann, W.K., Current transformers and relays for high-speed differential protection with particular reference to offset transient currents, AIEE Trans., 59, 481488, 1940. © 2004 by CRC Press LLC © 2004 by CRC Press LLC
29. Concordia, C. and Rothe, F.S., Transient characteristics of current transformers during faults, AIEE Trans., 66, 731734, 1947. 30. IEEE Power Engineering Society, Transient Response of Current Transformers, Special Publication 76 CH 1130-4 PWR, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1976. 31. IEEE, Guide for the Application of Current Transformers Used for Protective Relaying Purposes, IEEE C37.110-1996, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1996. 32. Sykes, J.A., A New Technique for High Speed Transformer Fault Protection Suitable for Digital Computer Implementation, IEEE Paper No. C72 429-9, presented at Power Engineering Society Summer Meeting, San Francisco, 1972. 33. Thorp, J.S. and Phadke, A.G., A Microprocessor-Based, Voltage-Restrained, Three-Phase Transformer Differential Relay, presented at Proceedings of the Southeastern Symposium on System Theory, Blacksburg, VA, April 1982, pp. 312316. 34. Thorp, J.S. and Phadke, A.G., A new computer based, flux restrained, current differential relay for power transformer protection, IEEE Trans., PAS-102, 36243629, 1983. 35. Inagaki, K., Higaki, M., Matsui, Y., Kurita, K., Suzuki, M., Yoshida, K., and Maeda, T., Digital protection method for power transformers based on an equivalent circuit composed of inverse inductance, IEEE Trans. Power Delivery, 3, 15011510, 1998. 36. General Electric Co., Transformer Differential Relay with Percentage and Harmonic Restraint Types BDD 15B, BDD16B, Document GEH-2057F, GE Protection and Control, Malvern, PA. 37. Bertula, G., Enhanced transformer protection through inrush-proof ratio differential relays, Brown Boveri Review, 32, 129133, 1945. 38. Giuliante, A. and Clough, G., Advances in the Design of Differential Protection for Power Transformers, presented at 1991 Georgia Tech. Protective Relaying Conference, Atlanta, 1991, pp. 112. 39. Hegazy, M., New principle for using full-wave rectifiers in differential protection of transformers, IEE Proc., 116, 425428, 1969. 40. Dmitrenko, A.M., The use of currentless pauses for detuning differential protection from transient imbalance currents, Elektrichestvo, No. 1, 55–58, January 1979 (in Russian). 41. Robertson, D., Ed., Power System Protection Reference Manual — Reyrolle Protection, Oriel Press, London, 1982. 42. Edgeley, R.K. and Hamilton, F.L., The application of transductors as relays in protective gear, IEE Proc., 99, 297, 1952. 43. Michelson, E.L., Rectifier relay for transformer protection, AIEE Trans., 64, 252254, 1945. 44. Podgornyi, E.V. and Ulianitskii, E.M., A comparison of principles for detuning differential relays from transformer inrush currents, Elektrichestvo, No. 10, 26–32, October 1969 (in Russian). 3.9 Causes and Effects of Transformer Sound Levels Jeewan Puri In many cities today there are local ordinances specifying maximum allowable sound levels at commercial and residential property lines. Consequently, the sound energy radiated from transformers has become a factor of increasing importance to the neighboring residential areas. It is therefore appropriate that a good understanding of sound power radiation and its measurement principles be developed for appropriately specifying sound levels in transformers. An understanding of these principles can be helpful in minimizing community complaints regarding the present and future installations of transformers. 3.9.1 Transformer Sound Levels An understanding of the following basic principles is necessary to evaluate a sound source to quantify the sound energy. 3.9.1.1 Sound Pressure Level The main quantity used to describe a sound is the size or amplitude of the pressure fluctuations at a human ear. The weakest sound a healthy human ear can detect has an amplitude of 20 millionths of a pascal (20 Pa). A pressure change of 20 Pa is so small that it causes the eardrum to deflect a distance less than the diameter of a single hydrogen molecule. Amazingly, the ear can tolerate sound pressures more than a million times higher. Thus, if we measured sound in Pa, we would end up with some quite large, unmanageable numbers. To avoid this, another scale is used — the decibel or dB scale. The decibel is not an absolute unit of measurement. It is a ratio between a measured quantity and an agreed reference level. The dB scale is logarithmic and uses the hearing threshold of 20 Pa as the reference level. This is defined as 0 dB. A sound pressure level L p can therefore be defined as: L p = 10 log (P/P 0 ) 2 (3.9.1) where L p = sound pressure level, dB P 0 = reference level = 20 Pa One useful aspect of the decibel scale is that it gives a much better approximation of the human perception of relative loudness than the pascal scale. 3.9.1.2 Perceived Loudness We have already defined sound as a pressure variation that can be heard by a human ear. A healthy human ear of a young person can hear frequencies ranging from 20 Hz to 20 kHz. In terms of sound pressure level, audible sounds range from the threshold of hearing at 0 dB to the threshold of pain, which can be over 130 dB. Although an increase of 6 dB represents a doubling of the sound pressure, in actuality, an increase of about 10 dB is required before the sound subjectively appears to be twice as loud. The smallest change in sound level we can perceive is about 3 dB. The subjective or perceived loudness of a sound is determined by several complex factors. One such factor is that the human ear is not equally sensitive at all frequencies. It is most sensitive to sounds between 2 kHz and 5 kHz and less sensitive at higher and lower frequencies. 3.9.1.3 Sound Power A source of sound radiates energy, and this results in a sound pressure. Sound energy is the cause. Sound pressure is the effect. Sound power is the rate at which energy is radiated (energy per unit time). The sound pressure that we hear (or measure with a microphone) is dependent on the distance from the source and the acoustic environment (or sound field) in which sound waves are present. This in turn depends on the size of the room and the sound absorption characteristics of its wall surfaces. Therefore the measuring of sound pressure does not necessarily quantify how much noise a machine makes. It is necessary to find the sound power because this quantity is more or less independent of the environment and is the unique descriptor of the noisiness of a sound source. 3.9.1.4 Sound Intensity Level Sound intensity describes the rate of energy flow through a unit area. The units for sound intensity are watts per square meter. Sound intensity also gives a measure of direction, as there will be energy flow in some directions but not in others. Therefore, sound intensity is a vector quantity, as it has both magnitude and direction. On the other hand, pressure is a scalar quantity, as it has magnitude only. Usually we measure the intensity in a direction normal (at 90) to a specified unit area through which the sound energy is flowing. Sound intensity is measured as the time-averaged rate of energy flow per unit area. At some points of measurements, energy may be traveling back and forth. If there is no net energy flow in the direction of measurement, there will be no net recorded intensity. © 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.,
Page 139 and 140: FIGURE 3.3.5 Reactance-type LTC, in
Page 141 and 142: FIGURE 3.3.10 LTC with delta connec
Page 143 and 144: 3.3.5 Selection of Load Tap Changer
Page 145 and 146: FIGURE 3.3.19 Effect of the leakage
Page 147 and 148: References Goosen, P.V. , Transform
Page 149 and 150: If i 1 is the full-load current rat
Page 151 and 152: TABLE 3.4.1 Loading Recommendations
Page 153 and 154: 3.5.4 Three-Phase Transformer Conne
Page 155 and 156: 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: 230 kV 3 180 MVA 138 kV 5 CTR1 = 2
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 and 208: % VOLTAGE % VOLTAGE 100 BIL 90 50 3
Page 209 and 210: 29. Degeneff, R.C., Reducing Storag
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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