ABB REG670 Commissioning Manual page 66

Section 6
Calibrating injection based sensitive rotor earth fault protection
60
A fine measurement of the frequency of the injected signals is also performed.
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 one rotor pole (see Figure 8) and
earth. The injection is made to the generator and the measured complex
impedance is stored.
3. The one rotor pole (see Figure 8) 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.
Step 1
DC
C
rot
AC
REX 061
I
inj
IEC11000205 V1 EN-US
Figure 8: Different steps at calibration measurements
The sequence of the calibration session follows a scheme shown in the tool.
• Calibration sequence 1: The injection must be activated and the rotor must be
left with no impedance connected. The ICT now makes consecutive
measurements until the statistical error reaches an acceptable value. This is
graphically shown in a diagram. The user stops the sequence by acceptance of
the measurement. The result is stored for later calculations.
• Calibration sequence 2: A known resistor is connected between the rotor
winding and earth. The value of the resistance is the input to ICT. The ICT
now makes consecutive measurements until the statistical error reaches an
acceptable value. This is graphically shown in a diagram. The user stops the
sequence by acceptance of the measurement. The result is stored for later
calculations.
• Calibration sequence 3: The generator rotor winding is now directly connected
to earth. The ICT now makes consecutive measurements until the statistical
error reaches an acceptable value. This is graphically shown in a diagram. The
user stops the sequence by acceptance of the measurement. The result is stored
for later calculations.
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Step 2
DC
C
rot
AC
REX 061
I
inj
R
Test
1MRK 502 073-UEN A
Step 3
DC
C
rot
AC
REX 061
I
inj
IEC11000205-1-en.vsd
Commissioning manual