4. Check that the trip and alarm contacts operate according to the configuration logic.
5. Decrease the current slowly from operate value and note the reset value.
Depending on the power transformer phase shift/vector group (Yd (Wye/Delta) and
so on), the single-phase injection current may appear as differential current in one or
two phases and the operating value of the injected single-phase current will be
different.
6. Check in the same way the function by injecting current in phases B and C
respectively.
7. Inject a symmetrical three-phase current and note the operate value.
8. Connect the timer and set the current to twice the operate value.
9. Switch on the current and note the operate time.
10. Check in the same way the measuring circuits connected to the CTs on the LV side
and other current inputs to the transformer differential protection.
11. Finally check that trip information is stored in the event menu.
Information on how to use the event menu is found in the operator’s
manual.
12. If available on the test set, a second harmonic current of about 20% (assumes 15%
setting on I1/I2 ratio parameter) can be added to the fundamental frequency in phase
A. Increase the current in phase A above the pickup value measured in step 6. Repeat
test with current injection in phases B and C respectively.
The balancing of currents flowing into and out of the differential zone is checked by
primary injection testing.
Fifth harmonic blocking can be tested in a similar way.
For more detailed formulas, please refer to the Application manual.
11.3.1.2 Completing the test
Continue to test another function or end the test by changing the TESTMODE setting to
Disabled. Restore connections and settings to their original values, if they were changed
for testing purposes.
11.3.2 High impedance differential protection HZPDIF (87)
Prepare the IED for verification of settings outlined in Section
"Preparing the IED to
verify settings".
Section 11 1MRK 504 165-UUS -
Testing functionality by secondary injection
108 Transformer protection RET670 2.2 ANSI
Commissioning manual
To Next Page
Loading...
Need help?
General
