Figure Q2 shows a single line diagram of a power system and the associated data of this system are given in Table Q2. The pre-fault load current and A-Y transformer phase shift are neglected. (a) (b) If a Single Line-to-Ground (S-L-G) fault occurs at Bus 5 and the pre-fault voltage is 1.0 pu, calculate the subtransient fault current in Ampere. (c) (d) Using base of 100 MVA and 11 kV at generator G₁, construct the positive sequence, negative sequence and zero sequence networks with their corresponding component values indicated. (e) Recalculate (b) if the neutral on HV side of T3 is solidly grounded. Repeat part (b) with Line-to-line (L-L) fault. What will happen to L-L fault current in (d) if the neutral on the HV side of T3 is solidly grounded?

Figure Q2 shows a single line diagram of a power system and the associated data of this system are given in Table Q2. The pre-fault load current and A-Y transformer phase shift are neglected. (a) (b) If a Single Line-to-Ground (S-L-G) fault occurs at Bus 5 and the pre-fault voltage is 1.0 pu, calculate the subtransient fault current in Ampere. (c) (d) Using base of 100 MVA and 11 kV at generator G₁, construct the positive sequence, negative sequence and zero sequence networks with their corresponding component values indicated. (e) Recalculate (b) if the neutral on HV side of T3 is solidly grounded. Repeat part (b) with Line-to-line (L-L) fault. What will happen to L-L fault current in (d) if the neutral on the HV side of T3 is solidly grounded?

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

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Concept explainers

Fault Analysis

In an electrical engineering system, a fault is an abnormal electric current flowing through the system, and fault analysis is the study of these faults. For instance, a short-circuit is a fault where the live wire touches the ground or neutral wire. If a circuit is interrupted by a failure of a current-carrying wire then an open circuit fault occurs. The open-circuit faults are also called series faults. One or more phases or ground may be involved in a three-phase fault or may occur only between two phases. Current flows into the earth in case of a ground fault or earth fault. For most situations, the prospective short circuit current of a fault that is predictable can be calculated. To limit the loss of service because of a failure, the protective devices can detect fault conditions and operate circuit breakers and also other devices. All phases equally can be affected in a poly-phase system which is known as symmetric electrical fault. The asymmetric fault becomes more complicated to analyze if only some phases are affected. By using methods such as symmetrical components, the power system analysis of these types of faults is often simplified. The main objective of power system protection is to design, detect, and interrupt power system faults.

Question

Device
Generator G₁
Generator G₂
Generator G3
Transformer Ti
Transformer T2
Transformer T3
Line 1
Line 2
Capacity Voltage
(MVA)
(kV)
100
11
50
11
50
11
70
132/11
70
132/11
70
132/11
Table Q2
X' X₁ X₂
(pu)
X"
(pu) (pu)
0.15
0.4
0.12
0.35
0.12
0.35
0.07
0.07
0.07
Xo
(pu) (pu)
0.12
0.06
0.1
0.05
0.1
0.05
0.07
0.07
0.07
0.07
0.07
0.07
35 52
35 92
35 92
35 92
70 92
70 92
Xn
(pu)
0.035

Q2
Figure Q2 shows a single line diagram of a power system and the associated data of this system
are given in Table Q2. The pre-fault load current and A-Y transformer phase shift are
neglected.
(a)
(b)
If a Single Line-to-Ground (S-L-G) fault occurs at Bus 5 and the pre-fault voltage is
1.0 pu, calculate the subtransient fault current in Ampere.
(c)
(d)
(e)
Using base of 100 MVA and 11 kV at generator G₁, construct the positive sequence,
negative sequence and zero sequence networks with their corresponding component
values indicated.
G₁
Recalculate (b) if the neutral on HV side of T3 is solidly grounded.
Repeat part (b) with Line-to-line (L-L) fault.
What will happen to L-L fault current in (d) if the neutral on the HV side of T3 is
solidly grounded?
Bus 1
T₁
Bus 4
Line 1
Line 2
Figure Q2
Bus 5
T2
T3
Bus 2
Bus 3
G₂
G3

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