1
1
,
stat
stat
N
Z
j C
R
eq
ω
=
+
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.
In order to perform the assessment, the first reference impedance, which is calculated
during the tentative calibration is assumed as an evaluation of the stator impedance to
ground.
2
2
Re
1
Re
1
stat
Z
fR
fX
≅
+
IECEQUATION17025 V2 EN-US
The assessment of the calibration is positive if:
500
1000
stat
Z
Ω ≤
≤
Ω
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.
ICT performs again consecutive measurements until the statistical error reaches an
acceptable value. This is graphically shown in a diagram.
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 values from IED button.
ICT performs again consecutive measurements until the statistical error reaches an
acceptable value. This is graphically shown in a diagram.
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.
Check the Calibration result field to make sure that all tests have been passed.
12.1. If a failure is indicated during one or more check(s), follow the instructions/tips
provided by the ICT in the Calibration result field.
12.2. If these tips do not solve the issue, then contact ABB Support.
Section 7
1MRK 502 067-UEN B
Calibrating injection based 100% stator earth fault protection
68
Commissioning manual
