ABB REC670 Applications Manual page 138

Section 7
Differential protection
132
Table 17: 1 A channels: input with minimum operating down to 40 mA
Operating Stabilizing
voltage resistor R
TripPickup
ohms
20 V 500
40 V 1000
60 V 1500
80 V 2000
100 V 2500
150 V 3750
200 V 5000
Table 18: 5 A channels: input with minimum operating down to 100 mA
Operating Stabilizing
voltage resistor R1
TripPickup
ohms
20 V 200
40 V 400
60 V 600
80 V 800
100 V 1000
150 V 1500
200 V 2000
The current transformer saturation voltage must be at least 2 ˣ TripPickup to have
sufficient operating margin. This must be checked after calculation of TripPickup.
When the R value has been selected and the TripPickup 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 14.
å
= × + +
IP n IR ( Ires lmag
EQUATION1747 V1 EN-US
where:
n is the CT ratio
IP primary current at IED pickup,
Table continues on next page
Operating Stabilizing
current level resistor R
1 A ohms
0.040 A --
0.040 A --
0.040 A 600
0.040 A 800
0.040 A 1000
0.040 A 1500
0.040 A 2000
Operating Stabilizing
current level resistor R1
5 A ohms
0.100 A 100
0.100 A 200
0.100 A 300
0.100 A 400
0.100 A 500
0.100 A 750
0.100 A 1000
)
1MRK 511 401-UUS A
Operating
current level
1 A
--
--
0.100 A
0.100 A
0.100 A
0.100 A
0.100 A
Operating Stabilizing
current level resistor R1
5 A ohms
0.200 A --
0.200 A 100
0.200 A 150
0.200 A 200
0.200 A 250
0.200 A 375
0.200 A 500
Bay control REC670 2.2 ANSI
Application manual
Operating
current level
5 A
--
0.400
0.400 A
0.400 A
0.400 A
0.400 A
0.400 A
(Equation 14)