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