Minimum ohms can be difficult to adjust due to the small value
compared to the total value.
Normally the voltage can be increased to higher values than the calculated
minimum
U>Trip
with a minor change of total operating values as long as this is
done by adjusting the resistor to a higher value. Check the sensitivity calculation
below for reference.
Table 10:
1 A channels: input with minimum operating down to 40 mA
Operating
voltage
U>Trip
Stabilizing
resistor R
ohms
Operating
current level
1 A
Stabilizing
resistor R
ohms
Operating
current level
1 A
20 V
500
0.040 A
--
--
40 V
1000
0.040 A
--
--
60 V
1500
0.040 A
600
0.100 A
80 V
2000
0.040 A
800
0.100 A
100 V
2500
0.040 A
1000
0.100 A
150 V
3750
0.040 A
1500
0.100 A
200 V
5000
0.040 A
2000
0.100 A
Table 11:
5 A channels: input with minimum operating down to 100 mA
Operating
voltage
U>Trip
Stabilizing
resistor R1
ohms
Operating
current level
5 A
Stabilizing
resistor R1
ohms
Operating
current level
5 A
Stabilizing
resistor R1
ohms
Operating
current level
5 A
20 V
200
0.100 A
100
0.200 A
--
--
40 V
400
0.100 A
200
0.200 A
100
0.400
60 V
600
0.100 A
300
0.200 A
150
0.400 A
80 V
800
0.100 A
400
0.200 A
200
0.400 A
100 V
1000
0.100 A
500
0.200 A
250
0.400 A
150 V
1500
0.100 A
750
0.200 A
375
0.400 A
200 V
2000
0.100 A
1000
0.200 A
500
0.400 A
The current transformer saturation voltage must be at least 2 ˣ
U>Trip
to have
sufficient operating margin. This must be checked after calculation of
U>Trip
.
When the R value has been selected and the
U>Trip
value has been set, the
sensitivity of the scheme
IP
can be calculated. The IED sensitivity is decided by
the total current in the circuit according to equation
.
(
)
IP
n IR Ires
lmag
= ×
+
+
å
EQUATION1747 V1 EN-US
(Equation 12)
1MRK 505 388-UEN B
Section 6
Differential protection
Busbar protection REB650 2.2 IEC
77
Application manual
Summary of Contents for REB650
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