10.4.4 Four step negative sequence overcurrent protectionNS4PTOC GUID-EB1A8DFD-5BAC-4024-ADA2-D9BE7A2B50A0 v2Prepare the IED for verification of settings as outlined in section "Preparing fortest" in this chapter.GUID-F7AA2194-4D1C-4475-8853-C7D064912614 v4When inverse time overcurrent characteristic is selected, theoperate time of the stage will be the sum of the inverse time delayand the set definite time delay. Thus, if only the inverse time delayis required, it is important to set the definite time delay for thatstage to zero.GUID-F973601F-BC67-4E4F-A4CA-BE6253E2FB92 v3Procedure1. Connect the test set for injection of three-phase currents and voltages to theappropriate CT and VT inputs of the IED.2. Inject pure negative sequence current, that is, phase currents with exactlysame magnitude, reversed sequence and exactly 120° phase displaced into theIED with an initial value below negative sequence current pickup level. Nooutput signals should be activated. Check under NS4PTOC function ServiceValues that correct I2 magnitude is measured by the function.3. Set the injected negative sequence polarizing voltage slightly larger than theset minimum polarizing voltage (default 5 % of Ub) and set the injectioncurrent to lag the voltage by an angle equal to the set reference characteristicangle (180° - AngleRCA) if the forward directional function is selected.If reverse directional function is selected, set the injection current to lag thepolarizing voltage by an angle equal to RCA.4. Increase the injected current and note the value at which the studied step ofthe function operates.5. Decrease the current slowly and note the reset value.6. Block lower set steps when testing higher set steps according to theinstructions that follow.7. Connect a trip output contact to a timer.8. Set the injected current to 200% of the operate level of the tested step, switchon the current and check the time delay.For inverse time curves, check the operate time at a current equal to 110% ofthe operate current in order to test parameter txmin.9. Check that all operate and start contacts operate according to theconfiguration (signal matrixes)10. Reverse the direction of the injected current and check that the step does notoperate.11. Check that the protection does not operate when the polarizing voltage iszero.12. Repeat the above-described tests for the higher set steps.13. Finally, check that start and trip information is stored in the event menu.Section 10 1MRK 505 372-UEN ATesting functionality by secondary injection94 Busbar protection REB670 2.2 IECCommissioning manual
