4.3 Inverse-Time Overcurrent Protection (ANSI 51, 67)
409
7UM62 Manual
C53000-G1176-C149-3
Trip Time
Characteristics As
Per ANSI
As per ANSI/IEEE (see also Figures 4-2 and 4-3)
The trip times for I/I
p
≥
20 are identical to those for I/I
p
= 20.
Pickup Threshold
Approx. 1.10 · I
p
Dropout Threshold
Approx. 1.05 · I
p
for I
p
/I
N
≥
0.3
corresponds to approx. [0.95 · pickup
threshold]
Tolerances
Pickup Currents I
p
1 % of setting value, or 50 mA
1
)
Voltage Threshold U<
1 % of setting value, or 0.5 V
Trip Time for 2
≤
I/I
p
≤
20
5 % of reference (calculated) value + 1 %
current tolerance, respectively 40 ms
Influencing
Variables for
Pickup
Power Supply Direct Voltage in Range
0.8
≤
U
PS
/ U
PS nominal
≤
1.15
1 %
Temperature in Range
23 °F
≤ ϑ
amb
≤
131 °F
0.3 % / 10 °F
–5 °C
≤ ϑ
amb
≤
55 °C
0.5 % / 10 K
Frequency in Range
0.95
≤
f/f
N
≤
1.05
< 1 %
1
) For I
N
= 1 A, divide all limits and increments by 5.
t
8.9341
I I
p
⁄
(
)
2.0938
1
–
---------------------------------------
0.17966
+
è
ø
ç
÷
æ
ö
D
⋅
=
INVERSE
VERY INVERSE
EXTREMELY INVERSE
For all Characteristics
t
= Trip time in seconds
D
= Setting value of the time multiplier
I
= Fault Current
I
p
= Setting value of the pickup current
DEFINITE INVERSE
MODERATELY INV.
t
0.0103
I I
p
⁄
(
)
0.02
1
–
----------------------------------
0.0228
+
è
ø
ç
÷
æ
ö
D
⋅
=
t
3.922
I I
p
⁄
(
)
2
1
–
---------------------------
0.0982
+
è
ø
ç
÷
æ
ö
D
⋅
=
t
5.64
I I
p
⁄
(
)
2
1
–
---------------------------
0.02434
+
è
ø
ç
÷
æ
ö
D
⋅
=
t
0.4797
I I
p
⁄
(
)
1.5625
1
–
---------------------------------------
0.21359
+
è
ø
ç
÷
æ
ö
D
⋅
=
[s]
[s]
[s]
[s]
[s]
