ABB REG670 Applications Manual page 159

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
Operating Stabilizing
voltage resistor R
U>Trip
ohms
80 V 2000
100 V 2500
150 V 3750
200 V 5000
Table 24: 5 A channels: input with minimum operating down to 100 mA
Operating Stabilizing
voltage resistor R1
U>Trip
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 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 22.
å
= × + +
IP n IR ( Ires
EQUATION1747 V1 EN
where:
n is the CT ratio
IP primary current at IED pickup,
IR IED pickup current (U>Trip/SeriesResistor)
Ires is the current through the voltage limiter and
ΣImag is the sum of the magnetizing currents from all CTs in the circuit (for example, 4 for restricted
earth fault protection, 2 for reactor differential protection, 3-5 for autotransformer differential
protection).
It should be remembered that the vectorial sum of the currents must be used (IEDs,
Metrosil and resistor currents are resistive). The current measurement is insensitive to
DC component in fault current to allow the use of only the AC components of the fault
current in the above calculations.
Operating Stabilizing
current level 1 resistor R
A ohms
0.040 A 800
0.040 A 1000
0.040 A 1500
0.040 A 2000
Operating Stabilizing
current level 5 resistor R1
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
lmag )
Section 7
Differential protection
Operating
current level 1
A
0.100 A
0.100 A
0.100 A
0.100 A
Operating Stabilizing
current level 5 resistor R1
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
(Equation 22)
Operating
current level 5
A
--
0.400
0.400 A
0.400 A
0.400 A
0.400 A
0.400 A
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