ABB REG670 2.0 IEC Commissioning Manual page 79

1MRK502053-UEN B
Generator protection REG670 2.0 IEC
Commissioning manual
Calibrating injection based 100% stator earth fault protection
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 to the generator neutral
point in parallel with the stator neutral point resistor. The value of the resistance
is input to ICT. 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 neutral point is now directly connected to
the earth, that is, the neutral point resistor is short-circuited. 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.
After the three measurements, ICT calculates the complex factors k1 and k2. The
reference impedance RefR1 + jRefX1 is also calculated. After this the values are
downloaded to the parameter setting part of the PCM600 tool. From PCM600 the
setting can be downloaded to IED.
During the three measurements described above a check is made that there are
sufficient changes in the measured impedance in order to guarantee that there is no
primary fault from the beginning or other problems due to the installation or
calibration procedure.
Now the reference impedance is derived for one operational state. It might be
necessary to make measurements to derive reference impedance for other operational
cases. For information on this, see Commissioning below.
Commissioning
There is a possibility to have up to five different reference impedances. The need to
change the reference impedance is that there will be different operating conditions for
the generator:
• Generator stand still
• Generator running up, not synchronized to the network (circuit breaker open)
• Generator normal operation (circuit breaker closed)
It might therefore be necessary to find reference impedances for different operation
states. In the commissioning part of ICT this can be done. For each operation state of
interest a measurement calibration as above is performed. If the reference impedance
differs from the first one, calculated under the calibration session, the new reference
impedance is stored by the command; Submit to Parameter setting. It is possible to
store up to five different reference impedances to be used at different operation states
of the generator.
ICT also performs verification between the newly acquired and existing reference
impedance(s) and warn the user if the resulting estimated fault difference could cause
alarm or trip when one reference is shifted from another during operation.
Section 7
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