ABB REG670 Commissioning Manual page 70

Section 6
Calibrating injection based sensitive rotor earth fault protection
64
Installing
During the installation, several checks are performed about both status of the function
and levels of the injected current and voltage. The check of signal levels need the
setting of the gain according to the value that is selected in REX060.
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 the generator neutral point and ground.
The injection is made to the generator and the measured complex impedance is
stored.
3. The generator neutral point is directly short-circuited to the ground. 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
ANSI11000205 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 ground. The value of the resistance is the input to ICT. The ICT now makes
consecutive measurements until the statistical error reaches an acceptable value.
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Step 2
DC
C
rot
AC
REX 061
I
inj
R
Test
1MRK 502 073-UUS A
Step 3
DC
C
rot
AC
REX 061
I
inj
ANSI11000205_1_en.vsd
Commissioning manual