Siemens 7UT51

8
Time Overcurrent Protection (50HS and 50/51)
7UT51 v3
104 PRIM-2330C
Figure 8.2 Very Inverse Time Overcurrent Characteristic Curves
.05 .1 1 10 100 1000
.01
.1
1
10
100
1000
Time (in seconds)
Multiples of Pickup Current ( )I/I
p
19.138
2.0
()I/I
p
- 1
+ 0.48258
× TD
t =
Multiples of Pickup Current ( )I/I
p
7UT51
Version 3.0
Time Overcurrent Characteristic Curves for
Protective Relay
.01
.1
1
10
100
1000
.05 .1 1 10 100 1000
TD TD
I/I
p
t
= time dial setting ( 0.5 32.0, steps of 0.01)
= current in multiples of pickup
= operating time in seconds
≤≤
Time (in seconds)
Very
Inverse
Time Dial Setting
0.7
0.5
10
7
5
3
2
1.5
1
Time value tolerance is ± 5% for > 2.I/I
p
32
20
15