[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

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the rated-voltage tap position. In some cases (e.g., transformers equipped with reactor-type on-load tap changers), a tap position other than the rated may be used if the transformer produces maximum sound levels at this position. 2 O 5 6 3.9.4.2 Principal Radiating Surface for Measurements The principal radiating surface is that from which the sound energy is emanating toward the receiver locations. The location of the radiating surface is determined based on the proximity of the cooling equipment to the transformer. For transformers with no cooling equipment (or with cooling equipment mounted less than 3 m from the transformer tank) or dry-type transformers with enclosures provided with cooling equipment (if any) inside the enclosure, the principal radiating surface is obtained by taking the vertical projection of a string contour surrounding the transformer and its cooling equipment (if any), as shown in Figure 3.9.2. The vertical projection begins at the tank cover and terminates at the base of the transformer. Separate radiating surfaces for the transformer and its cooling equipment are determined if the cooling equipment is mounted more than 3 m from the transformer tank. The principal radiating surface for the cooling equipment is determined by taking the vertical projection of the string perimeter surrounding the cooling equipment, as shown in Figure 3.9.3. The vertical projection begins at the top of the cooling structure and terminates at its base. 3.9.4.3 Prescribed Contour Location for Measurements All sound-level measurements are made on a prescribed contour located 0.3 m away from the radiating surface. The location of this contour depends on the radiating surface as determined by the proximity of the cooling equipment to the transformer, as shown in Figure 3.9.2 and Figure 3.9.3. The location of the prescribed contours above the base of the transformer shall be at half the tank height for transformer tanks 2.5 m high. 3.9.4.4 Measuring Positions on Prescribed Contour The first microphone position is located on the prescribed contour opposite the main tank drain valve. Proceeding in a clockwise direction (as viewed from the top of the transformer) additional measuring positions on the prescribed contour are located no more than 1 m apart. The minimum number of measurements as stipulated in IEEE C57.12.90 or IEEE C57.12.91 for North American practice are taken on each prescribed contour. These standards specify that sound-level measurements shall be made with and without the cooling equipment in operation. IEC 60076-10 standard should be consulted for European practices, which are slightly different. 3.9.4.5 Sound-Pressure-Level Measurements A-weighted sound-pressure-level measurements are the most commonly used method for determining sound levels in transformers. Sound pressure measurements are quite sensitive to the ambient sound levels on the test floor. Therefore, appropriate corrections for the ambient sound level and reflected sound from the surrounding surfaces must also be quantified to determine the true sound level of the transformer. It is recommended that acceptable ambient sound level conditions should be met for obtaining reliable measurements on transformers. For this reason, industry standards specify that A-weighted ambient sound pressure levels must be measured immediately before and after the measurements on the transformer. The ambient noise level readings are taken at each microphone position on the prescribed contours with the transformer and cooling equipment (if any) de-energized. These measurements are used to correct the measurements made on the transformer. The magnitude of this correction depends on the difference between the ambient and the transformer sound levels. This difference should not be less than 5 dB for a valid measurement. No correction is necessary if the ambient sound level is more than 10 dB lower than the transformer sound level. FIGURE 3.9.2 Typical microphone positions for sound measurement on transformers having cooling auxiliaries mounted either directly on the tank or on a separate structure spaced
H 2m 1. Vertical Forced Air 2. Principal Radiating Surface 3. Prescribed Contour 1 2 6 FIGURE 3.9.3 Typical microphone positions for sound measurement on cooling auxiliaries mounted on a separate structure spaced 3 m from the principal radiating surface of the transformer. (From IEC 60076-10. With permission.) L pAi = A-weighted sound-pressure level measured at the ith position and corrected for the ambient noise level per Table 1, dB (reference = 20Pa) N = total number of measuring positions on the prescribed contour K = environmental correction for the influence of reflected sound and ambient sound level, dB (IEEE and IEC standards should be consulted for details) 3.9.4.6 Sound-Intensity Measurements The equipment for these measurements has only recently emerged in the industry. By definition, the A- weighted sound-intensity measurements provide a measure of sound power radiated in watts through a unit area per unit time. This type of measurement yields a vector quantity that represents the sound energy radiated in a direction normal to the principal radiating surface of the transformer. The noise-intensity measuring probes use two matched microphones that respond to sound pressure so that the readings taken by them does not differ by more than 1.5 dB at any location. From the measured sound intensity levels, L IAi , at each position of the prescribed contour, an A- weighted average sound intensity level in decibels, L IA , can be calculated using Equation 3.9.11: 3 4 5 4. Horizontal Forced Air 5. Horizontal Boundaries of Principal Radiating Surface 6. Vertical Boundaries of Principal Radiating Surface L IA = 10 log [1/N 100 .1 Lia ] dB (3.9.11) where L IA = A-weighted average sound-intensity level, dB (reference = 10 –12 W/m 2 ) L ia = A-weighted sound-intensity level measured at the ith position for the ambient noise level, (reference = 10 –12 W/m 2 ) N = total number of measuring positions on the prescribed contour Unlike sound pressure, the noise-intensity measurements are not influenced by the ambient noise level, provided that the ambient noise remains constant as the measurements are taken around the prescribed contour. Under such conditions, noise-intensity measurements can be made in ambient sound level even higher than the sound level of the transformer. For this reason, this type of measurement is especially suitable for transformers designed for very low noise levels. It should be recognized that, at this time, the transformer industry’s experience in sound intensity measurement is rather limited. Actual measurements published in CIGRE publications have demonstrated that the reliability of the sound-intensity measurements depends on the difference L between the average sound intensity and pressure measurements made by the same probes. This work suggests that for optimum results, L should not be more than 8dB. 3.9.4.7 Calculation of Sound <strong>Power</strong> Level It is necessary to calculate sound pressure levels at property lines located away from the transformer in order to demonstrate compliance with the local ordinances. Sound power level provides a measure of the total sound energy radiated by a transformer. With this quantity, the sound pressure levels at any desired distance (outside the prescribed contour) from the transformer can be calculated. Since sound-pressure or sound-intensity measurements yield the same numerical result, the following equations can be used to calculate sound power levels in decibels from the measured sound-pressure or sound-intensity levels. or L WA = L IA + 10 log (S) (3.9.12) L WA = L pA + 10 log (S) (3.9.13) where S = area of the radiating surface, m 2 L WA = 10 log (W/W 0 ) = A-weighted sound power level, dB (W 0 = 10 –12 W) L pA = A-weighted average sound pressure level, dB (reference = 20 Pa) L IA = A-weighted average sound intensity level, dB (reference = 10 –12 W/m 2 ) The calculation of effective radiating surface area S is also a function of the distance at which the sound measurements were made. IEEE or IEC standards can be consulted for details. 3.9.4.8 Sound-Pressure-Level Calculations at Far Field Receiver Locations Sound-level requirements at a specific receiver location in the far field play a major role in specifying sound levels for transformers. The following basic method can be considered for estimating transformer sound pressure levels for simple installations. These calculations provide an accurate estimate of transformer noise emissions at distances roughly greater than twice the largest dimension of the transformer. N i1 © 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
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 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: FIGURE 3.9.1 Measurement of pressur
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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