ABB REG670 - Page 159

Operating
voltage
U>Trip
Stabilizing
resistor R
ohms
Operating
current level 1
A
Stabilizing
resistor R
ohms
Operating
current level 1
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 24: 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
22.
( )IP n IR Ires lmag= × + +
å
EQUATION1747 V1 EN (Equation 22)
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.
1MRK 502 071-UEN - Section 7
Differential protection
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 153
Application manual