transformer differential functions T2WPDIF (87T) or T3WPDIF (87T) areunblocked.2. Connect the test set for injection of three-phase currents to the current terminalsof the IED, which are connected to the CTs on the HV side of the powertransformer.3. Increase the current in phase A until the protection function operates and note theoperating current.4. Check that the trip and alarm contacts operate according to the configurationlogic.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 inone or two phases and the operating value of the injected single-phase currentwill be different.6. Check in the same way the function by injecting current in phases B and Crespectively.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 LVside 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 theoperator’s manual.12. If available on the test set, a second harmonic current of about 20% (assumes15% setting on I1/I2 ratio parameter) can be added to the fundamental frequencyin phase A. Increase the current in phase A above the pickup value measured instep 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 checkedby primary injection testing.Fifth harmonic blocking can be tested in a similar way.For more detailed formulas, please refer to the Applicationmanual.13.3.1.2 Completing the test SEMOD54284-86 v5Continue to test another function or end the test by changing the TESTMODE setting toDisabled. Restore connections and settings to their original values, if they werechanged for testing purposes.Section 13 1MRK 502 073-UUS ATesting functionality by secondary injection142 Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062Commissioning manual
