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4.3
Inverse-Time Overcurrent Protection (ANSI 51, 67)
Pickup and Time
Multiplier Ranges/
Resolutions
Trip Time
Characteristics As
Per IEC
Tolerances
Influencing
Variables for
Pickup
7UM62 Manual
C53000-G1176-C149-3
Pickup Current
Time Multipliers for 51
IEC Characteristics
Time Multiplier for 51
ANSI Characteristics
Undervoltage Release
As per IEC 60255-3, Section 3.5.2 or BS 142 (See also Figure 4-1)
NORMAL INVERSE (Type A)
VERY INVERSE (Type B)
EXTREMELY INV. (Type C)
≥ 20 are identical to those for I/I
The trip times for I/I
p
Pickup Threshold
Dropout Threshold
Pickup Currents I
p
Voltage Threshold U<
Trip Time for 2 ≤ I/I
≤ 20
p
Power Supply Direct Voltage in Range
0.8 ≤ U
/ U
PS
PS nominal
Temperature in Range
23 °F ≤ ϑ
≤ 131 °F
amb
–5 °C ≤ ϑ
≤ 55 °C
amb
Frequency in Range
0.95 ≤ f/f
≤ 1.05
N
Harmonic Currents
– Up to 10 % 3rd Harmonics
– Up to 10 % 5th Harmonics
1
) For I
= 1 A, divide all limits and increments by 5.
N
4.3 Inverse-Time Overcurrent Protection (ANSI 51, 67)
51
0.50 A to 20.00 A
T
0.05 s to 3.20 s
p
or ∞ (delay does not expire)
D
0.50 to 15.00
or ∞ (delay does not expire)
U<
10.0 V to 125.0 V
t
=
t
=
t
=
For All Characteristics
t
T
p
I
I
p
Approx. 1.10 · I
Approx. 1.05 · I
1 % of setting value, or 50 mA
1 % of setting value, or 0.5 V
5 % of reference (calculated) value + 1 %
current tolerance, respectively 40 ms
≤ 1.15
1 %
0.3 % / 10 °F
0.5 % / 10 K
< 1 %
< 1 %
< 1 %
1
) (Increments 0.05 A)
(Increments 0.01 s)
(Increments 0.01)
(Increments 0.1 V)
0.14
⋅
--------------------------------- - T
[s]
p
0.02
(
⁄
)
I I
1
–
p
13.5
⋅
-------------------------- - T
[s]
p
1
(
⁄
)
I I
1
–
p
80
⋅
-------------------------- - T
[s]
p
2
(
⁄
)
I I
–
1
p
Trip time in seconds
Setting value of the time multiplier
Fault current
Setting value of the pickup current
= 20.
p
p
≥ 0.3
for I
/I
p
p
N
1
)
1
)
407
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