ABB REG670 Commissioning Manual page 87

1MRK 502 073-UEN A
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Commissioning manual
Calibrating injection based 100% stator earth fault protection
1
=
Z
stat
1
+
R eq ,
N
IECEQUATION17024 V1 EN-US
If the capacitance to ground of the stator is unknown, a calibration resistance
with tentative value equal to 1000 Ω can be used. This tentative value shall be
assessed after the calibration procedure is completed.
The first reference impedance, which is calculated during the tentative
calibration is assumed as an evaluation of the stator impedance to ground.
»
Z Re fZ 1
stat
IECEQUATION17025 V1 EN-US
The assessment of the calibration is positive if:
W £ £
500 Z 1000
stat
IECEQUATION17026 V1 EN-US
If the assessment is negative, the calibration shall be repeated with a
calibration resistance close to the absolute value of the estimated stator
impedance to ground.
6. Type the value in ohm of the calibration resistance in the real part of the
Connected impedance field and type 0 in the imaginary part field.
This informs the ICT that we have connected a pure resistive impedance that
has a value equal to the typed one.
7. In the ICT toolbar, select the Start reading values from IED button.
8. Once again, wait until the stability criteria is fulfilled, then select the Submit
button.
The result is stored for later calculations. ICT automatically shifts to the third
calibration tab, Step 3: Measurement 3.
If readings are not stable during the step, a warning to repeat
the step may be suggested; the step shall be repeat in order to
avoid that the calibration fails.
9. Remove the known fault resistance attached earlier and apply a short circuit
instead.
10. In the ICT toolbar, select the Start reading valuesfrom IED button.
11. When the stability criteria are fulfilled, select the Submit button once again.
The result is stored for calculations. ICT automatically shifts to the fourth
calibration tab, Step 4: Save Calibration Factors. Here the newly calculated
complex factors k1 and k2 as well as the reference impedance 1 are presented.
The values of these parameters are calculated by ICT on the basis of the three
measurement steps described above.
12. ICT performs several checks on the measurement results of each steps in
order to verify that there are sufficient changes in the measured impedances
(too low changes may be related to a grounded system at the beginning of the
calibration) and that no problem affected the installation and calibration
procedure.
w
j C
stat
W
Section 7
81