9-34 L90 Line Current Differential System GE Multilin9.5 SINGLE-POLE TRIPPING 9 THEORY OF OPERATION99.5SINGLE-POLE TRIPPING 9.5.1 OVERVIEWa) INTRODUCTIONSingle pole operations make use of many features of the relay. At the minimum, the trip output, recloser, breaker control,open pole detector, and phase selector must be fully programmed and in service; and either protection elements or digitalinputs representing fault detection must be available for successful operation. When single pole trip-and-reclose is requiredoverall control within the relay is performed by the trip output element. This element includes interfaces with pilot aidedschemes, the line pickup, breaker control, and breaker failure elements.Single pole operations are based on use of the phase selector to identify the type of the fault, to eliminate incorrect faultidentification that can be made by distance elements in some circumstances and to provide trip initiation from elements thatare not capable of any fault type identification, such as high-set negative-sequence directional overcurrent element. Thescheme is also designed to make use of the advantages provided by communications channels with multiple-bit capacitiesfor fault identification.Figure 9–13: SINGLE-POLE OPERATIONThe trip output element receives requests for single and three pole trips and three pole reclose initiation, which it then pro-cesses to generate outputs that are used to:• Determine whether a single or three pole operation should be performed.• Initiate tripping of breaker poles A, B and C, either individually or as a group.• Initiate breaker failure protection for phases A, B and C, either individually or as a group.• Notify the open pole detector when a single pole operation is imminent.• Initiate either single or three pole reclosing.Block specific protection elementsProtectionelementsInputs SettingSettingSettingOutputsSettingInputsSettingSettingLine pickupReclose requestForcethree-ooleoperationThree-poletriprequestThree-poletripTripA or B or CSingle-poletripSingle-poletrip requestSLGfaultedphaseAGAR FORCE 3-PMulti-phaseVoidBGCGSingle-poleoperationThree-poleoperationPermissionResetTripAR Initiate 3-PolePilot-aidedschemesCommunicationschannels837026A5.CDRTrip outputVoltsandampsPhase selectorResetoutputInitiate breakerfailureBreakercontrolBreaker1 and 2pole stateBreaker1 and 2out-of-serviceVoltsandampsRecloserCLOSE 1CLOSE 1CLOSE 2CLOSE 2OperatorSettingSettingInputsOutputsInitiateInitiateMulti-phaseFault locatorOpenpoledetectorSettingBreaker 1 and 2
