[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

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FIGURE 2.2.26 Typical Type 1 loop-feed system. (By permission of ABB Inc., Raleigh, NC.) FIGURE 2.2.29 Radial-style live front. (By permission of Pacific Gas & Electric Company, San Francisco, CA.) FIGURE 2.2.27 Typical Type 2 loop-feed system. (By permission of ABB Inc., Raleigh, NC.) FIGURE 2.2.30 Loop-style live front. (By permission of Pacific Gas & Electric Company, San Francisco, CA.) FIGURE 2.2.28 Single-phase live front. (By permission of Pacific Gas & Electric Company, San Francisco, CA.) six-bushing units also allow the construction of duplex pad-mounted units that can be used to supply small three-phase loads along with the normal single-phase residential load. In those cases, the service voltage is four-wire, three-phase, 120/240 V. Cabinets for single-phase transformers are typically built in the clamshell configuration with one large door that swings up, as shown in Figure 2.2.26 and Figure 2.2.27. Older units were manufactured with two doors, similar to the three-phase cabinets. New installations are almost universally dead front; however, live-front units (see Figure 2.2.28) are still purchased for replacements. These units are also built with clamshell cabinets but have an internal box-shaped insulating barrier constructed around the primary connections. 2.2.8.2 Three-Phase Pad-Mounted Transformers Three-phase pad-mounted transformers are typically applied to serve commercial and industrial threephase loads from underground distribution systems. Traditionally, there have been two national standards that detailed requirements for pad-mounted transformers — one for live front (ANSI C57.12.22) and one for dead front (IEEE C57.12.26). The two standards have now been combined into one for all pad mounts, designated IEEE C57.12.34. 2.2.8.3 Live Front Live-front transformers are specified as radial units and thus do not come with any fuse protection. See Figure 2.2.29. The primary compartment is on the left, and the secondary compartment is on the right, with a rigid barrier separating them. The secondary door must be opened before the primary door can be opened. Stress-cone-terminated primary cables rise vertically and connect to the terminals on the end of the high-voltage bushings. Secondary cables rise vertically and are terminated on spades connected to the secondary bushings. Units with a secondary of 208Y/120 V are available up to 1000 kVA. Units with a secondary of 480Y/277 V are available up to 2500 kVA. Although not detailed in a national standard, there are many similar types available. A loop-style live front (Figure 2.2.30) can be constructed by adding fuses mounted below the primary bushings. Two primary cables are then both connected to the bottom of the fuse. The loop is then made at the terminal of the high-voltage bushing, external to the transformer but within its primary compartment. 2.2.8.4 Dead Front Both radial- and loop-feed dead-front pad-mounted transformers are detailed in the standard. Radialstyle units have three primary bushings arranged horizontally, as seen in Figure 2.2.31. Loop-style units have six primary bushings arranged in a V pattern, as seen in Figure 2.2.32 and Figure 2.2.33. In both, © 2004 by CRC Press LLC © 2004 by CRC Press LLC
FIGURE 2.2.31 Radial-style dead front. (By permission of Pacific Gas & Electric Company, San Francisco, CA.) FIGURE 2.2.34 Mini three-phase in clamshell cabinet. (By permission of ABB Inc., Raleigh, NC.) FIGURE 2.2.32 Small loop-style dead front. (By permission of ABB Inc., Raleigh, NC.) FIGURE 2.2.33 Large loop-style dead front. (By permission of ABB Inc., Raleigh, NC.) the primary compartment is on the left, and the secondary compartment is on the right, with a rigid barrier between them. The secondary door must be opened before the primary door can be opened. The primary cables are terminated with separable insulated high-voltage connectors, commonly referred to as 200-A elbows, specified in IEEE Standard 386. These plug onto the primary bushings, which can be either bushing wells with an insert, or they can be integral bushings. Bushing wells with inserts are preferred, as they allow both the insert and elbow to be easily replaced. Units with a secondary of 208Y/ 120 V are available up to 1000 kVA. Units with a secondary of 480Y/277 V are available up to 2500 kVA. 2.2.8.5 Additional Ratings In addition to what is shown in the national standards, there are other variations available. The smallest size in the national standards is the 75 kVA unit. However, 45 kVA units are also manufactured in the normal secondary voltages. Units with higher secondary voltages, such as 2400 and 4160Y/2400, are manufactured in sizes up to 3750 kVA. There is a new style being produced that is a cross between singleand three-phase units. A small three-phase transformer is placed in a six-bushing loop-style clamshell cabinet, as seen in Figure 2.2.34. These are presently available from 45 to 150 kVA in both 208Y/120 and 480Y/277V secondaries. 2.2.8.6 Pad-Mount Common Elements 2.2.8.6.1 Protection Most distribution transformers include some kind of primary overcurrent protection. For a detailed discussion, see Section 2.2.13, Transformer Protection. 2.2.8.6.2 Primary Conductor Pad-mounted transformers are designed to be connected to an underground distribution system that utilizes 200-A-class equipment. The primary is most often #2 or 1/0 cables with 200-A elbows or stress cones. It is recommended that larger cables such as 4/0 not be used with the 200-A elbows. The extra stiffness of 4/0 cable makes it very difficult to avoid putting strain on the elbow-bushing interface, leading to premature elbow failures. 2.2.8.6.3 Pad Pads are made out of various materials. The most common is concrete, which can be either poured in place or precast. Concrete is suitable for any size pad. Pads for single-phase transformers are also commonly made out of fiberglass or polymer-concrete. 2.2.8.6.4 Enclosure There are two national standards that specify the requirements for enclosure integrity for pad-mounted equipment: C57.12.28 (ANSI/NEMA, 1999) for normal environments and C57.12.29 (ANSI, 1991) for coastal environments. The tank and cabinet of pad-mounted transformers are commonly manufactured out of mild carbon steel. When applied in corrosive areas, such as near the ocean, they are commonly made out of 300- or 400-series stainless steel. In general, 300-series stainless steel will outperform 400- series stainless steel, which significantly outperforms mild carbon steel in corrosive applications. © 2004 by CRC Press LLC © 2004 by CRC Press LLC
Page 1 and 2: ELECTRIC POWER TRANSFORMER ENGINEER
Page 3 and 4: I wish to recognize the interest of
Page 5 and 6: Contents 1 Theory and Principles Ch
Page 7 and 8: 1.3 Equivalent Circuit of an Iron-C
Page 9 and 10: designer starts to make a design fo
Page 11 and 12: • Transient voltages generated du
Page 13 and 14: the transformer’s bushings and, m
Page 15 and 16: % regulation = [(V NL - V FL )/V FL
Page 17 and 18: In core-form transformers, the wind
Page 19 and 20: FIGURE 2.1.14 Layer windings (singl
Page 21 and 22: the transformer design, which may b
Page 23 and 24: consumer’s service circuit is a d
Page 25 and 26: FIGURE 2.2.3 Single-phase transform
Page 27 and 28: is installed so that the tank never
Page 29 and 30: above which persons might be burned
Page 31 and 32: FIGURE 2.2.16 Two-bushing subway. (
Page 33: carbon steel or the very expensive
Page 37 and 38: FIGURE 2.2.36 Complete transformer
Page 39 and 40: voltage in each winding simultaneou
Page 41 and 42: mounted transformers can have arres
Page 43 and 44: V S + V S I V L Z=R+jX a) V L V S V
Page 45 and 46: Z = jX (2.3.19) 0.7 Then the curren
Page 47 and 48: X1 L* X1 S =X1 L X2 L* X3 L* a) S L
Page 49 and 50: 150 V(%) 100 50 0 -50 40 80 T(s) 12
Page 51 and 52: 2.3.8.1.2 Series Connection • The
Page 53 and 54: A six-pulse single-way transformer
Page 55 and 56: The degree of coupling also influen
Page 57 and 58: where I h = current for the hth har
Page 59 and 60: In the case of liquid-filled transf
Page 61 and 62: FIGURE 2.4.21 A 36-pulse system mad
Page 63 and 64: Vacuum-pressure encaps ulated — T
Page 65 and 66: FIGURE 2.6.1 Typical wiring and sin
Page 67 and 68: a) H1 b) Ip X2 FLUX H2 LEAKAGE FLUX
Page 69 and 70: and for CTs is TCF = RCF - (PA/2600
Page 71 and 72: RCF x Bx Bt RCF t - RCF 0 co
Page 73 and 74: 2000 1000 5% Vex BANDWITH FROM NOMI
Page 75 and 76: This may be more useful when operat
Page 77 and 78: also some uncertainty in repeatabil
Page 79 and 80: FIGURE 2.6.25 Standard two-element
Page 81 and 82: 2.7 Step-Voltage Regulators Craig A
Page 83 and 84: Source Bypass Switch Source Bypass
Page 85 and 86:
2.7.4 Theory A step-voltage regulat
Page 87 and 88:
FIGURE 2.7.22 Equalizer winding inc
Page 89 and 90:
TABLE 2.7.4 Increase in Ampere Load
Page 91 and 92:
References IEEE, Standard Requireme
Page 93 and 94:
300% FIGURE 2.8.4 Schematic of a co
Page 95 and 96:
TABLE 2.8.1 Typical Sizing Workshee
Page 97 and 98:
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
Page 103 and 104:
References 1. Sola/Hevi-Duty Corp.,
Page 105 and 106:
FIGURE 2.9.5 Typical phase-reactor
Page 107 and 108:
FIGURE 2.9.10 Two generator arrange
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• Overloading of lines • Increa
Page 111 and 112:
FIGURE 2.9.23 34-kV, 25-MVAR (per p
Page 113 and 114:
V 90 ( X X ) s T (2.9.10a) where,
Page 115 and 116:
Therefore, Line reactive losses = (
Page 117 and 118:
ate of rise of transient-recovery v
Page 119 and 120:
the LLCR is provided in IEEE Std. C
Page 121 and 122:
aluminum shielding, i.e., an oil-im
Page 123 and 124:
Leo J. Savio ADAPT Corporation Ted
Page 125 and 126:
3.1.2.2.2 Heat Dissipation A second
Page 127 and 128:
FIGURE 3.2.1 Solid-type bushing. ma
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1.6 cm. This means that most of the
Page 131 and 132:
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
Page 137 and 138:
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 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 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 237 and 238:
Page 239 and 240:
Page 241:
TABLE 3.14.13 Relevant Documents fo
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[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

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