Power System Analysis and Design (MindTap Course List)
6th Edition
ISBN: 9781305632134
Author: J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher: Cengage Learning
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Textbook Question
Chapter 7, Problem 7.14P
Equipment ratings for the five-bus power system shown in Figure 7.15 are as follows:
Generator G1:    50 MVA, 12kV,Â
Generator G2: 100Â MVA, 15 kV,
Transformer T1: 50 MVA, 10 kV
Transformer T2: 100 MVA, 15 kV
Each 138-kV line:
A three-phase short circuit occurs at bus 5, where the prefault voltage is 15 kV. Prefault load current is neglected. (a) Draw the positive-sequence reactance diagram in unit on a 100-MVA, 15-kV base in the zone of generator G2. Determine (b) the ThĂ©venin equivalent at the fault, (c) the subtransient fault current in per unit and in kA rms, and (d) contributions to the fault from generator G2 and from transformer T2. 
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Students have asked these similar questions
Three zones of a single-phase circuit are identified in the figure. The zones are connected by
transformers T₁ and T2, whose ratings are also shown. Using base values of 100 kVA and 240 volts in
zone 1, draw the per-unit circuit and determine the per-unit impedances and the per-unit source
voltage. Then calculate the load current both in per-unit and in amperes. Transformer winding
resistances and shunt admittance branches are neglected.
Zone 1
Zone 2
Vs = 220/0° volts
3---38
T,
30 KVA
240/480 volts
M 0.10 p.u.
Xoa
Xune = 2 fl
T
T₂
20 kVA
460/115 volts
Xeg = 0.10 p.u.
Zone 3
ww
Zload = 0.9 - 10.20
Three zones of a single-phase circuit are identified shown in Figure below. The zones are connected by
transformers T1 and T2, whose ratings are also shown. Using base values of 33 kVA and 232 volts in zone 1,
Find:
1- Draw the per-unit circuit including the per-unit impedances and the per-unit source voltage.
2- Calculate the load current both in per-unit and in amperes (actual or original value).
Vs
Zone 1
232.940° Vs
G.
38
T₁
30 KVA
240/480 volts
Xeq = 0.10 p.u.
Zone 2
Xiine
=
4 Ω
T₂
20 KVA
460/115 volts
Zload =
Xea
= 0.10 p.u.
Zone 3
u
1+j2.2 Ω
2
Q2. The single-line diagram of a simple three-bus power system
is shown in Figure-2. Each generator is represented by an emf
behind the sub-transient reactance. All impedances are
expressed in per unit on a common MVA base. All resistances
and shunt capacitances are neglected. The generators are
operating on no load at their rated voltage with their emfs in
phase. A three-phase fault occurs at bus 3 through a fault
impedance of Zf = j0.19 per unit.
(i) Using Th'evenin's theorem, obtain the impedance to the
point of fault and the fault current in
(ii) Determine the bus voltages
per
unit.
) j0.05
j0.075
j0.75
2
j0.30
j0.45
Figure-2: Single line diagram of the
power system network for Q2
3
Chapter 7 Solutions
Power System Analysis and Design (MindTap Course List)
Ch. 7 - Even though the fault current is not symmetrical...Ch. 7 - The amplitude of the sinusoidal symmetrical ac...Ch. 7 - Equipment ratings for the four-bus power system...Ch. 7 - Equipment ratings for the five-bus power system...Ch. 7 - Prob. 7.22PCh. 7 - A three-phase circuit breaker has a 15.5-kV rated...Ch. 7 - Prob. 7.32P
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