4.3 Inverse-Time Overcurrent Protection (ANSI 51, 67)
411
7UM62 Manual
C53000-G1176-C149-3
Figure 4-3
Trip Time Characteristics of the Inverse-time Overcurrent Protection, as per ANSI/IEEE
D [s]
I
/
I
p
1
2
5
10
15
0.5
2
3
5
10
20
0.3
0.1
500
20
10
2
0.05
5
0.2
0.5
1
t [s]
30
100
200
3
50
1
EXTREMELY INVERSE
t
5 64
,
I I
p
⁄
(
)
2
1
–
----------------------------
0 02434
,
+
è
ø
ç
÷
ç
÷
æ
ö
D
⋅
=
[s]
D [s]
I
/
I
p
1
2
5
15
0.5
1
2
3
5
10
20
DEFINITE INVERSE
[s]
t
0 4797
,
I I
p
⁄
(
)
1 5625
,
1
–
---------------------------------------------
0 21359
,
+
è
ø
ç
÷
ç
÷
æ
ö
D
⋅
=
0.3
0.1
500
20
10
2
0.05
5
0.2
0.5
1
t [s]
30
100
200
3
50
10
t
Trip time in seconds
D
Setting value of the time factor
I
Fault current
I
p
Setting value of the pickup current