By default the measured absolute impedance is plotted, however there are
several items that can be viewed when monitoring. To see these, select the
available quantities under the Viewed quantity drop-down menu under the
Monitoring tab.
4. Observe the fault conductance while applying known faults.
Both the calibration factors and the reference that is used can be verified this
way. In some cases though, it is desired to be able to measure/view other
quantities.
5. Select Fault conductance in the Viewed quantity drop-down menu.
The fault conductance is equal to 1/fault resistance, and is more suitable to
view when no faults or very small faults are applied/measured.
Due to the fact that no fault theoretically equals infinite fault resistance and
viewing this only plots unreliable values, it is better to view the fault
conductance, which is zero in this case.
As no fault is applied, the measured fault conductance must be close to zero.
Confirm this by viewing the graph.
It may be necessary to zoom in or out to properly view the measurements. For
instructions on this, see
Editing features in graph .
6. Apply for example 10kΩ fault resistance.
6.1. Make sure that it is correctly measured.
6.2. Try to change the Viewed quantity to Fault resistance as 10kΩ is
relatively small.
You should be able to measure approximately 10kΩ here. If you choose
to view fault conductance, the measurement corresponds to
approximately 1×10
-4
Mho.
7. Apply another known fault, say 1kΏ and verify that it is measured correctly.
8. When you are completely sure that the function measures correctly, stop the
measurements and remove any applied faults.
Previously it was verified that the function measures correctly by applying
known faults and observing the graph during monitoring. Besides measuring
the fault size a trip indication is required when a large fault is measured to
prevent that a damage to the generator occurs. To allow the specific function
to issue a trip indication, it must first be enabled:
8.1. Select the Enable Function Tripping button in the ICT toolbar.
8.2. Choose Yes in the pop-up message.
ICT now writes this to IED.
8.3. By default the trip level is set to 1kΩ. In other words, if the fault
resistance is lower, then the function issue trips.
9. Verify the measurements by applying various faults.
Trip indication shall be visible in the ICT toolbar.
10. Verify that TRIP and ALARM signals are connected to tripping/alarming/
signaling/communication in accordance with the scheme design.
It is very important that the Function Tripping is Enabled under the
following situations:
1MRK 502 029-UEN A Section 10
Calibrating injection based sensitive rotor earth fault protection
115
Installation and commissioning manual
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