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5.102
SEL-421 Relay
Instruction Manual
Date Code 20171021
Protection Functions
Inverse-Time Overcurrent Elements
Table 5.65
Equations Associated With IEC Curves
Curve Type
Operating Time
Reset Time
Figure
C1 (Standard Inverse)
C2 (Very Inverse)
C3 (Extremely Inverse)
C4 (Long-Time Inverse)
C5 (Short-Time Inverse)
T
p
TD
0.14
M
0.02
1
–
--------------------
•
=
T
r
TD
13.5
1 M
2
–
----------------
•
=
T
p
TD
13.5
M 1
–
--------------
•
=
T
r
TD
47.3
1 M
2
–
----------------
•
=
T
p
TD
80
M
2
1
–
----------------
•
=
T
r
TD
80
1 M
2
–
----------------
•
=
T
p
TD
120
M 1
–
--------------
•
=
T
r
TD
120
1 M
–
--------------
•
=
T
p
TD
0.05
M
0.04
1
–
--------------------
•
=
T
r
TD
4.85
1 M
2
–
----------------
•
=
Summary of Contents for SEL-421-4
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