[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

Recommendations

Info

A A’ Thus the kVA rating of a step-voltage regulator is determined considering its range of voltage regulation. Single-phase voltage regulators are available in the common ratings shown in Table 2.7.3, where all entries are understood to be for 10% range of voltage regulation. Vsystem B TABLE 2.7.3 Commonly Available Ratings for Single-Phase Voltage Regulators FIGURE 2.7.10 Phasor diagram of closed-delta-connected voltage regulators. B SOURCE C SOURCE A SOURCE FIGURE 2.7.11 <strong>Power</strong> connection of closed-delta-connected voltage regulators. 2.7.3 Ratings SL L C’ +10% Regulation Regulator 3 S L The rated-load current of a step-voltage regulator is determined by the following equation: S C B’C’ Voltage is 15% Higher than Vsystem (BC) 3load IRated (2.7.1) VL–L 3 If the regulators are used in a single-phase circuit, four-wire grounded-wye circuit, or connected in a wye configuration in a three-wire system, the rated voltage of the regulator would be V L–L / 3 . If the regulators were connected in an open- or closed-delta configuration for a three-wire system, the rated voltage of the regulator would be V L–L . As a result, the kVA rating of the regulator would be determined by the following equation: SL Regulator 1 S kVA = (V Rated I Rated per-unit range of regulation)/1000 (2.7.2) SL L B’ Regulator 2 C LOAD B LOAD A LOAD Rated Volts BIL, kV Rated, kVA Load Current, A 2,500 60 50 200 75 300 100 400 125 500 167 668 250 1000 333 1332 416 1665 5,000 75 50 100 75 150 100 200 125 250 167 334 250 500 333 668 416 833 7,620 95 38.1 50 57.2 75 76.2 100 114.3 150 167 219 250 328 333 438 416 548 500 656 667 875 833 1093 13,800 95 69 50 138 100 207 150 276 200 414 300 552 400 14,400 150 72 50 144 100 288 200 333 200 432 300 576 400 667 463 833 578 19,920 150 100 50 200 100 333 200 400 200 667 300 833 400 © 2004 by CRC Press LLC © 2004 by CRC Press LLC
2.7.4 Theory A step-voltage regulator is a tapped autotransformer. To understand how a regulator operates, one can start by comparing it with a two-winding transformer. Figure 2.7.12 is a basic diagram of a transformer with a 10:1 turns ratio. If the primary winding or V source has 1000 V applied, the secondary winding or V load will have an output of 100 V (10%). These two independent windings can be connected so that their voltages aid or oppose one another. A voltmeter connected across the output terminals measures either the sum of the two voltages or the difference between them. The transformer becomes an autotransformer with the ability to raise (Figure 2.7.13) or lower (Figure 2.7.14) the primary or system voltage by 10%. This construction is similar to a “Type A” single-phase step-voltage regulator, as described later in thissection. + VSOURCE = 1000 + VLOAD= 100 - - FIGURE 2.7.15 Tap-changer position indicator. 10 : 1 FIGURE 2.7.12 <strong>Transformer</strong> with 10:1 turns ratio. + - + VSOURCE = 1000 VLOAD = 1100 - FIGURE 2.7.13 Step-up autotransformer. FIGURE 2.7.14 Step-down autotransformer. + - + VSOURCE = 1000 VLOAD = 900 - In a voltage regulator, the equivalent of the high-voltage winding in a two-winding transformer would be referred to as the shunt winding. The low-voltage winding would be referred to as the series winding. The series winding is connected to the shunt winding in order to boost or buck the applied or primary voltage approximately 10%. The polarity of its connection to the shunt winding is accomplished by the use of a reversing switch on the internal motor-driven tap changer. Eight approximately 1 1 / 4 % taps are added to the series winding to provide small voltage-adjustment increments. To go even further to provide fine voltage adjustment, such as 16 approximate 5/8% tap steps, a center tapped bridging reactor (preventive autotransformer) — used in conjunction with two movable contacts on the motorized tap changer — is utilized. In all, there are 33 positions that include neutral, 16 lower positions (1L, 2L, 3L, 4L, etc.), and 16 raise positions (1R, 2R, 3R, 4R, etc.). Figure 2.7.15 illustrates a dial that indicates the arrangement of the tap positions. It is common practice to have the tap changer located in the same compartment as the core and coil. Dielectric practices consider the oil and insulation degradation due to the arc by-products. Figure 2.7.16 shows a typical load-break tap changer used in a single-phase step-voltage regulator. The process of moving from one voltage-regulator tap to the adjacent voltage-regulator tap consists of closing the circuit at one tap before opening the circuit at the other tap. The movable tap-changer contacts move through stationary taps alternating in eight bridging and eight nonbridging (symmetrical) positions. Figure 2.7.17 shows the two movable tap-changer contacts on a symmetrical position, with the center tap of the reactor at the same potential. This is the case at tap position N (neutral) and all evenly numbered tap positions. An asymmetrical position, as shown in Figure 2.7.18, is realized when one tap connection is open before transferring the load to the adjacent tap. At this juncture, all of the load current flows through one-half of the reactor, magnetizing the reactor, and the reactance voltage is introduced into the circuit for about 25 to 30 msec during the tap change. Figure 2.7.19 shows the movable contacts in a bridging position; voltage change is one-half the 1 1 / 4 % tap voltage of the series winding because of its center tap and movable contacts located on adjacent stationary contacts. This is the case at all oddly numbered tap positions. Voltage phasor relations shown in Figure 2.7.20 represent a tap change. In this figure, S–SL represents source or unregulated voltage, and sections of the series winding are represented by S–TAP 1 and TAP 1–TAP 2. In operating the tap changer from TAP 1 to TAP 2, the load or regulated voltage has the following successive values: © 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 and 34: carbon steel or the very expensive
Page 35 and 36: FIGURE 2.2.31 Radial-style dead fro
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: Source Bypass Switch Source Bypass
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
Page 99 and 100: FIGURE 2.8.20A Performance of a rid
Page 101 and 102: • 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
Page 109 and 110: • 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
Page 129 and 130: 1.6 cm. This means that most of the
Page 131 and 132: where HS = steady-state bushing ho
Page 133 and 134: the conductivity of the water-solub
Page 135 and 136:
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
show all

[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

Create successful ePaper yourself

Delete template?

Save as template?