13.3.2.2 Completing the test SEMOD55257-73 v4Continue 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.13.3.3 Generator differential protection GENPDIF (87G) SEMOD155702-45 v4Prepare the IED for verification of settings outlined in Section "Preparing the IED toverify settings".13.3.3.1 Verifying the settings SEMOD155702-49 v41. Go to Main menu/Test/Function test modes/Differential protection and makesure all other functions, configured to the same current transformer inputs as thegenerator differential protection, are set off. Make sure that the generatordifferential function is unblocked.2. Connect the test set for injection of three-phase current to the current IEDs, whichare connected to the CTs on the HV side of the generator.3. Increase the current in phase A until the protection function operates and note theoperating current.4. Check that trip and alarm contacts operate according to the configuration logic.5. Decrease the current slowly from operate value and note the reset value.6. Check in the same way the function by injecting current in phases B and C.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 functioning of the measuring circuits connected to theCTs on the neutral point side of the generator.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% (assumes 15%setting on I1/I2 ratio parameter) can be added to the fundamental tone in phase A.Increase the current in phase A above the pickup value measured in step 3.Repeat test with current injection in phases B and C respectively.Fifth-harmonic blocking can be tested in a similar way.The balancing of currents flowing into and out of the differential zone is typicallychecked by primary testing.Section 13 1MRK 502 073-UUS ATesting functionality by secondary injection144 Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062Commissioning manual
