5.112
SEL-421 Relay
Instruction Manual
Date Code 20171021
Protection Functions
Inverse-Time Overcurrent Elements
Figure 5.86
IEC Short-Time Inverse—C5
10
20
30
40
50
60
70
80
90
100
1
2
3
4
5
6
7
8
9
.1
.2
.3
.4
.5
.6
.7
.8
.9
.01
.02
.03
.04
.05
.06
.07
.08
.09
100
1
2
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4
5 6 7 8 9
.5 .6 .7 .8 .9
90
80
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10
Time in
Sec
onds
Time in
Cy
cles 60 Hz
(50 Hz
)
6000 (5000)
3000 (2500)
1500 (1250)
600 (500)
300 (250)
150 (125)
60 (50)
30 (25)
15 (12.5)
6 (5)
3 (2.5)
Multiples of Pickup
0.05
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
Summary of Contents for SEL-421-4
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