[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

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FIGURE 2.9.2 Modern fully encapsulated reactor. FIGURE 2.9.3 Gapped iron-core oil-immersed reactor. encapsulated construction became the design of choice because its improved mechanical characteristics enabled the reactors to withstand higher fault currents. Conversely, high-voltage (HV) series reactors were initially oil-immersed shielded-core designs. However, beginning in the early 1970s, the requirements of these applications were also met by fully encapsulated dry-type air-core designs. Due to such developments, the latest revision of IEEE C57.16-1996 (R 2001), the series-reactor standard, is a now a dry-type air-core-reactor standard only. The construction technology employed for modern shunt reactors, on the other hand, is more dependent on the applied voltage. Transmission-class shunt reactors are of oil-immersed construction, whereas tertiary connected, or lower-voltage direct-connect shunt reactors, utilize either dry-type air-core or oilimmersed construction. Hence ANSI/IEEE C57.21-1990 (R 1995) covers both oil-immersed and drytype air-core shunt reactors. A review of modern reactor applications is presented in the following subsections. 2.9.2.2 Current-Limiting Reactors Current-limiting reactors are now used to control short-circuit levels in electrical power systems covering the range from large industrial power complexes to utility distribution networks to HV and EHV transmission systems. Current-limiting reactors (CLR) are primarily installed to reduce the short-circuit current to levels consistent with the electromechanical withstand level of circuit components (especially transformers and circuit breakers) and to reduce the short-circuit voltage drop on bus sections to levels that are consistent with insulation-coordination practice. High fault currents on distribution or transmission systems, if not limited, can cause catastrophic failure of distribution equipment and can present a serious threat to the FIGURE 2.9.4 Dry-type iron-core reactor (water cooled). safety of operating crews. In summary, current-limiting reactors are installed to reduce the magnitude of short-circuit currents in order to achieve one or more of the following benefits: • Reduction of electromechanical loading and thermal stresses on transformer windings, thus extending the service life of transformers and associated equipment © 2004 by CRC Press LLC © 2004 by CRC Press LLC
FIGURE 2.9.5 Typical phase-reactor connection. • Improved stability of primary bus voltage during a fault event on a feeder • Reduction of current-interrupting duty of feeder circuit breakers • Reduction of line-to-line fault current to levels below those of line-to-ground faults or vice versa • Protection of distribution transformer and all other downstream power equipment and devices from the propagation of initial fast-front voltage transients due to faults and/or circuit-breaker operations • Reduced need for downstream protection devices such as reclosers, sectionalizers, and currentlimiting fuses • Ability to obtain complete control over the steady-state losses by meeting any specified Q-factor for any desired frequency, a feature that is particularly important for networks where high harmonic currents are to be damped without increasing the fundamental-frequency loss • Increase in system reliability FIGURE 2.9.6 345-kV phase reactors. Current-limiting reactors can be installed at different points in the power network, and as such, they are normally referred to by a name that reflects their location/application. The most common nomenclatures are: • Phase reactors, installed in series with incoming or outgoing lines or feeders • Bus-tie reactors, used to tie together two otherwise independent buses • Neutral-grounding reactors, installed between the neutral of a transformer and ground • Duplex reactors, installed between a single source and two buses 2.9.2.2.1 Phase Reactors Figure 2.9.5 shows the location of phase reactors in the feeder circuits of a distribution system. Currentlimiting reactors can also be applied at transmission-voltage levels, as shown in Figure 2.9.6, depicting 345-kV, 1100-A, 94.7-mH phase reactors installed in a U.S. utility substation. The main advantage of the illustrated configuration is that it reduces line-to-line and phase-to-ground short-circuit current to any desired level at a strategic location in the distribution or transmission system. Phase reactors are one of the most versatile embodiments of series-connected reactors in that they can be installed (1) in one feeder of a distribution system to protect one circuit or (2) at the output of a generator to limit fault contribution to the entire power grid or (3) anywhere in between. Any of the benefits listed in the Section 2.9.2.2, Current-Limiting Reactors, can be achieved with this type of currentlimiting reactor. The impedance of the phase reactor required to limit the 3 short-circuit current to a given value can be calculated using either Equation 2.9.1 or Equation 2.9.2. X CLR = V LL [(1/I SCA ) – (1/I SCB )]/ 3 (2.9.1) X CLR = V 2 LL [(1/MVA SCA ) – (1/MVA SCB )] (2.9.2) FIGURE 2.9.7 Typical bus-tie-reactor connection. where X CLR = reactance of the current limiting reactor, V LL = rated system voltage, kV I SCA or MVA SCA =required value of the short-circuit current or power after the installation of the phase reactor, kA or MVA, respectively I SCB or MVA SCB = available value of the short-circuit current or power before the installation of the phase reactor, kA or MVA, respectively 2.9.2.2.2 Bus-Tie Reactors Bus-tie reactors are used when two or more feeders and/or power sources are connected to a single bus and it is desirable to sectionalize the bus without losing operational flexibility. Figure 2.9.7 illustrates the arrangement. As in the case of phase reactors, bus-tie reactors may be applied at any voltage level. Figure 2.9.8, shows an example of a 230-kV, 2000-A, 26.54-mH bus-tie reactor installed in a U.S. utility substation. The advantages of this configuration are similar to those associated with the use of phase reactors. An added benefit is that if the load is essentially balanced on both sides of the reactor under normal operating conditions, the reactor has negligible effect on voltage regulation or system losses. The required reactor impedance is calculated using either Equation 2.9.1 or Equation 2.9.2 for 3 faults or Equation 2.9.3 for single line-to-ground faults. © 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
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
Page 99 and 100: FIGURE 2.8.20A Performance of a rid
Page 101 and 102: • Input frequency or frequency ra
Page 103: References 1. Sola/Hevi-Duty Corp.,
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
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FIGURE 3.5.4 Interconnected star-gr
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3.6.1.1 Standards ANSI standards fo
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ANSI standards. LTC control setting
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FIGURE 3.6.7 Discharging the capaci
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FIGURE 3.6.10 Standard switching-im
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voltage of the excited winding, rea
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FIGURE 3.6.18 Current, voltage, and
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TABLE 3.6.3 Transformer Short-Circu
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FIGURE 3.7.3 Control for voltage re
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FIGURE 3.7.6A Feeder with power-fac
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3. Circulating current (current bal
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FIGURE 3.7.10 Control block diagram
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Primary Current (Amps) 60 40 20 0 -
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current transformer having two prim
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87R1 87BL1 (A) Independent Harmonic
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Winding 1 Secondary Currents Data A
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Y Y 20 18 3 rd Harmonic CTR1=40 CTR
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230 kV 3 180 MVA 138 kV 5 CTR1 = 2
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29. Concordia, C. and Rothe, F.S.,
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FIGURE 3.9.1 Measurement of pressur
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H 2m 1. Vertical Forced Air 2. Prin
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Gade, S., Sound Intensity Instrumen
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nected. This steady-state voltage d
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where [A] = state matrix [B] = inpu
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where C = capacitance between the t
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L ijo = N i N j ijo (3.10.31) 1.4
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% VOLTAGE % VOLTAGE 100 BIL 90 50 3
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29. Degeneff, R.C., Reducing Storag
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All connections should be cleaned a
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6. Costs to set up and use a mobile
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Records of relay operation must be
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• Has heating occurred as the res
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a reference value) of the currents
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The next data-processing step is to
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temperature. As the transformer coo
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3.13.3.2 Instrument Transformers Th
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FIGURE 3.13.5 Analysis of bushing s
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temperature. Under abnormal conditi
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3.14.1.2 Accredited Standards Commi
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FIGURE 3.14.4 IEC technical-committ
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TABLE 3.14.2 Relevant Documents for
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TABLE 3.14.13 Relevant Documents fo
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