Sel 411L - Table 3.108 U.S. Time-Overcurrent Equations; Table 3.109 IEC Time-Overcurrent Equations

P.3.206
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
Selectable Time-Overcurrent Elements (51)
at the E51 = prompt are active. For example, if you want to use six inverse-
time overcurrent elements for your application, set E51 = 6. Inverse-time
overcurrent elements 01–06 become active.
Table 3.108 shows the five U.S. characteristics, and Table 3.109 shows the five
IEC characteristics. Each table shows the five operating time equations,
together with the five electromechanical reset characteristic equations.
Table 3.108 U.S. Time-Overcurrent Equations
a
a
T
P
= Operating Time.
T
R
= Reset Time.
TD = Time-Delay Setting.
M = Measured Current / Pickup Current.
Curve Type Operating Time Reset Time
U1 (Moderately Inverse)
U2 (Inverse)
U3 (Very Inverse)
U4 (Extremely Inverse)
U5 (Short-Time Inverse)
Tp TD 0.0226
0.0104
M
0.02
1–
----------------------+


=
T
R
TD
1.08
1M
2
–
----------------


=
Tp TD 0.180
5.95
M
2
1–
----------------+


=
T
R
TD
5.95
1M
2
–
----------------


=
Tp TD 0.0963
3.88
M
2
1–
----------------+


=
T
R
TD
3.88
1M
2
–
----------------


=
Tp TD 0.02434
5.64
M
2
1–
----------------+


=
T
R
TD
5.64
1M
2
–
----------------


=
Tp TD 0.00262
0.00342
M
0.02
1–
----------------------+


=
T
R
TD
0.323
1M
2
–
----------------


=
Table 3.109 IEC Time-Overcurrent Equations
Curve Type Operating Time Reset Time
C1 (Standard Inverse)
C2 (Very Inverse)
C3 (Extremely Inverse)
C4 (Long-Time Inverse)
C5 (Short-Time Inverse)
Tp TD
0.14
M
0.02
1–
----------------------


=
T
R
TD
13.5
1M
2
–
----------------


=
Tp TD
13.5
M1–
--------------


=
T
R
TD
47.3
1M
2
–
----------------


=
Tp TD
80
M
2
1–
----------------


=
T
R
TD
80
1M
2
–
----------------


=
Tp TD
120
M1–
--------------


=
T
R
TD
120
1M–
--------------


=
Tp TD
0.05
M
0.04
1–
----------------------


=
T
R
TD
4.85
1M
2
–
----------------


=