9.4
SEL-351A Relay
Instruction Manual
Date Code 20080213
Setting the Relay
Time-Overcurrent Curves
Time-Overcurrent Curves
The following information describes the curve timing for the curve and time
dial settings made for the time-overcurrent elements (see
). The time-overcurrent relay curves in
–
conform to IEEE C37.112-1996 IEEE Standard Inverse-Time Characteristic
Equations for Overcurrent Relays.
where:
T
p
= Operating time in seconds
T
R
= Electromechanical induction-disk emulation reset time in
seconds (if you select electromechanical reset setting)
TD = Time-dial setting
M = Applied multiples of pickup current [for operating time
(T
p
), M > 1; for reset time (T
R
), M
≤
1]
Table 9.3
Equations Associated With U.S. Curves
Curve Type
Operating Time
Reset Time
Figure
U1 (Moderately Inverse)
U2 (Inverse)
U3 (Very Inverse)
U4 (Extremely Inverse)
U5 (Short-Time Inverse)
Table 9.4
Equations Associated With IEC Curves
(Sheet 1 of 2)
Curve Type
Operating Time
Reset Time
Figure
C1 (Standard Inverse)
C2 (Very Inverse)
C3 (Extremely Inverse)
T
p
TD
0.0226
0.0104
M
0.02
1
–
(
)
---------------------------
+
⎝
⎠
⎛
⎞
•
=
T
R
TD
1.08
1
M
2
–
(
)
---------------------
⎝
⎠
⎛
⎞
•
=
T
p
TD
0.180
5.95
M
2
1
–
(
)
---------------------
+
⎝
⎠
⎛
⎞
•
=
T
R
TD
5.95
1
M
2
–
(
)
---------------------
⎝
⎠
⎛
⎞
•
=
T
p
TD
0.0963
3.88
M
2
1
–
(
)
---------------------
+
⎝
⎠
⎛
⎞
•
=
T
R
TD
3.88
1
M
2
–
(
)
---------------------
⎝
⎠
⎛
⎞
•
=
T
p
TD
0.0352
5.67
M
2
1
–
(
)
---------------------
+
⎝
⎠
⎛
⎞
•
=
T
R
TD
5.67
1
M
2
–
(
)
---------------------
⎝
⎠
⎛
⎞
•
=
T
p
TD
0.00262
0.00342
M
0.02
1
–
(
)
---------------------------
+
⎝
⎠
⎛
⎞
•
=
T
R
TD
0.323
1
M
2
–
(
)
---------------------
⎝
⎠
⎛
⎞
•
=
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
–
(
)
---------------------
⎝
⎠
⎛
⎞
•
=
Summary of Contents for SEL-351A
Page 10: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 16: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 34: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 126: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 184: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 198: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 228: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 278: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 384: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 410: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 450: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 454: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 472: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 504: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 558: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 562: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 586: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 608: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...
Page 666: ...This page intentionally left blank Courtesy of NationalSwitchgear com ...