Schweitzer Engineering Laboratories SEL-387E - Time Overcurrent Curve Reference Information

3-52 Protection Functions Date Code 20080110
SEL-387E Instruction Manual
Time Overcurrent Curve Reference Information
tp = operating time in seconds
tr = electromechanical induction-disk emulation reset time in seconds
(if electromechanical reset setting is made)
TD = time-dial setting
M = applied multiples of pickup current [for operating time (tp), M>1; for reset time (tr), M≤1]
U.S. Moderately Inverse Curve: U1
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
+=
2
02.0
M1
08.1
•TDtr
1M
0104.0
0226.0•TDtp
U.S. Inverse Curve: U2
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
+=
2
2
M1
95.5
•TDtr
1M
95.5
180.0•TDtp
U.S. Very Inverse Curve: U3
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
+=
2
2
M1
88.3
•TDtr
1M
88.3
0963.0•TDtp
U.S. Extremely Inverse Curve: U4
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
+=
2
2
M1
67.5
•TDtr
1M
67.5
0352.0•TDtp
U.S. Short-Time Inverse Curve: U5
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
+=
2
02.0
M1
323.0
•TDtr
1M
00342.0
00262.0•TDtp
I.E.C. Class A Curve (Standard Inverse): C1
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
=
2
02.0
M1
5.13
•TDtr
1M
14.0
•TDtp
I.E.C. Class B Curve (Very Inverse): C2
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
=
2
M1
3.47
•TDtr
1M
5.13
•TDtp
I.E.C. Class C Curve (Extremely Inverse): C3
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
=
2
2
M1
0.80
•TDtr
1M
0.80
•TDtp
I.E.C. Long-Time Inverse Curve: C4
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
=
M1
0.120
•TDtr
1M
0.120
•TDtp
I.E.C. Short-Time Inverse Curve: C5
⎥
⎦
⎤
⎢
⎣
⎡
−
=
⎥
⎦
⎤
⎢
⎣
⎡
−
=
2
04.0
M1
85.4
•TDtr
1M
05.0
•TDtp