ABB REG670 2.0 IEC Commissioning Manual page 78

Section 7
Calibrating injection based 100% stator earth fault protection
72
injection frequency (e.g. due to accuracy of the REX060 hardware). Set manually the
actual frequency value measured by ICT in the IED via PST.Check that the selected
injection frequency setting on REX060 is equal to the FreqInjected setting in
parameter setting. Also verify that the measured injection frequency is reasonable and
continue by submitting the frequency value to parameter setting, then finish by writing
it to IED.
The high accuracy of this frequency is essential for proper operation of the protection
under different operating conditions.
Calibrating
The calibration is based on three measurement steps.
The sequence of the calibration measurements is shown in the figure below. The
connection of the fault resistance and short circuit is here shown for the case with
injection in the generator neutral point via the neutral point VT. The same principle is
valid for any other principles of injection; with LV neutral point resistor connected via
DT or injection via open delta connected VT group on the generator terminal, etc.
Step 1
C
stat
I
inj
+
R U
N
-
GUID-9E470F57-D670-430C-BD27-CBF11AF92D1E V1 EN
Figure 19: Different steps at calibration measurements
For other injection point alternatives the connection of the test resistance (step 2) and
short circuit (step 3) are made to the same points as shown in the figure above.
The sequence of the calibration session follows a scheme shown in the tool.
• Calibration sequence 1: The injection must be activated and the stator neutral
point must be left with no additional impedance connected in parallel with the
neutral point resistor. ICT now makes consecutive measurements until the
statistical error reaches an acceptable value. This is graphically shown in a
Step 2
C
stat
a
R R
inj test N
b
IEC11000044-1-en.vsd
1MRK502053-UEN B
Step 3
C
stat
I
inj
a
+
U R
inj N
-
b
Generator protection REG670 2.0 IEC
Commissioning manual
I
inj
a
+
U
inj
-
b