11.3.1.1 Verifying the settings
SEMOD54284-51 v11
1. Go to Main menu /Test /Function test modes /Differential protection and make sure that the
restricted earth fault protection, low impedance function REFPDIF (87N) is set to Disabled and that
the four step residual overcurrent function EF4PTOC (51N/67N) under Main menu /Test /Function
test modes /Current protection is set to Disabled, since they are configured to the same current
transformer inputs as the transformer differential protection. Make sure that the transformer
differential functions T2WPDIF (87T) or T3WPDIF (87T) are unblocked.
2. Connect the test set for injection of three-phase currents to the current terminals of the IED, which
are connected to the CTs on the HV side of the power transformer.
3. Increase the current in phase A until the protection function operates and note the operating
current.
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
SEMOD54284-86 v5
Continue to test another function or end the test by changing the TESTMODE setting to Disabled.
Restore connections and settings to the original values, if changed for testing purposes.
11.3.2 High impedance differential protection HZPDIF (87)
SEMOD55257-42 v3
Prepare the IED for verification of settings as outlined in section "Requirements" and section "Preparing
for test" in this chapter.
1MRK 504 165-UUS Rev. J Section 11
Testing functionality by secondary injection
Transformer protection RET670 97
Commissioning manual
© 2017 - 2021 Hitachi Power Grids. All rights reserved
To Next Page
Loading...
