ABB REG670 Commissioning Manual page 82

Section 7
Calibrating injection based 100% stator earth fault protection
76
need the setting of the UMaxEF according to the value that is selected in REX060:
this parameter is related to the gain of amplifiers of REX060.
A fine measurement of the frequency of the injected signals is also performed to be
able to detect properly interference conditions.
Calibrating
The calibration is based on three measurement steps.
1. The injection is made to the faultless generator and the measured complex
impedance is stored.
2. A known resistance is connected between the generator neutral point (see
Figure 18) and earth.
The injection is made to the generator and the measured complex impedance is
stored.
3. The generator neutral point (see Figure 18) is directly short-circuited to the
earth. The injection is made to the generator and the measured complex
impedance is stored.
The sequence of the calibration steps is driven by ICT and it is shown in the figure
below. The connection of the calibration resistance and short circuit is shown here
for the case with injection in the generator neutral point through the neutral point
VT and generator grounding through primary resistor.
Step 1
C
stat
I
inj
+
R U
N
-
GUID-9E470F57-D670-430C-BD27-CBF11AF92D1E V1 EN-US
Figure 18: Different steps at calibration measurements
There are other generator grounding methods and injection alternatives; the
injection can be performed through:
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Step 2
C
stat
a
R R
inj test N
b
IEC11000044-1-en.vsd
1MRK 502 073-UEN A
Step 3
C
stat
I
inj
a
+
U R
inj N
-
b
Commissioning manual
I
inj
a
+
U
inj
-
b