Time Seconds 10 5.0 4.0 3.0 2.0 1.0 60 .60 .50 .40 .30 .20 15 .15 1.5 3.0 5.0 10 15 30 30 Multiples of Relay Tap Setting 40 50 Figure 4.5 Time-delay overcurrent relay operating characteristic 1/2 Time Dial Setting 4.6 For the radial system shown in Figure 4.22, calculate the instantaneous and time-delay over- current relay settings at each bus. Assume the transformer must not be de-energized and that the relays at bus B are 'looking into' a transformer differential and do not need to coordinate with it. Assume any pickup tap is available, but use the relay characteristic of Figure 4.5. A B 1 2 100 A. ctr=30/1 ctr = 20/1 50 A. Rab Во Min. Fault = 3000 A. 2000 A. 1000 A. Max. Fault = 9000 A. 5000 A. 3000 A. Figure 4.22 System diagram for problem 4.6 4.7 The current in both instantaneous relays of problem 4.6 exceeds 100 A. Revise the CT ratios and recalculate both time-delay and instantaneous relay settings at buses A and B.
Time Seconds 10 5.0 4.0 3.0 2.0 1.0 60 .60 .50 .40 .30 .20 15 .15 1.5 3.0 5.0 10 15 30 30 Multiples of Relay Tap Setting 40 50 Figure 4.5 Time-delay overcurrent relay operating characteristic 1/2 Time Dial Setting 4.6 For the radial system shown in Figure 4.22, calculate the instantaneous and time-delay over- current relay settings at each bus. Assume the transformer must not be de-energized and that the relays at bus B are 'looking into' a transformer differential and do not need to coordinate with it. Assume any pickup tap is available, but use the relay characteristic of Figure 4.5. A B 1 2 100 A. ctr=30/1 ctr = 20/1 50 A. Rab Во Min. Fault = 3000 A. 2000 A. 1000 A. Max. Fault = 9000 A. 5000 A. 3000 A. Figure 4.22 System diagram for problem 4.6 4.7 The current in both instantaneous relays of problem 4.6 exceeds 100 A. Revise the CT ratios and recalculate both time-delay and instantaneous relay settings at buses A and B.
Power System Analysis and Design (MindTap Course List)
6th Edition
ISBN:9781305632134
Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Chapter12: Power System Controls
Section: Chapter Questions
Problem 12.4P
Related questions
Question
Please solve question 4.7 in detail and thank you
Transcribed Image Text:Time
Seconds
10
5.0
4.0
3.0
2.0
1.0
60
.60
.50
.40
.30
.20
15
.15
1.5
3.0
5.0
10 15
30
30
Multiples of Relay Tap Setting
40 50
Figure 4.5 Time-delay overcurrent relay operating characteristic
1/2
Time Dial Setting
Transcribed Image Text:4.6 For the radial system shown in Figure 4.22, calculate the instantaneous and time-delay over-
current relay settings at each bus. Assume the transformer must not be de-energized and that
the relays at bus B are 'looking into' a transformer differential and do not need to coordinate
with it. Assume any pickup tap is available, but use the relay characteristic of Figure 4.5.
A
B
1
2
100 A.
ctr=30/1
ctr = 20/1
50 A.
Rab
Во
Min. Fault = 3000 A.
2000 A.
1000 A.
Max. Fault = 9000 A.
5000 A.
3000 A.
Figure 4.22 System diagram for problem 4.6
4.7 The current in both instantaneous relays of problem 4.6 exceeds 100 A. Revise the CT ratios
and recalculate both time-delay and instantaneous relay settings at buses A and B.
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