9-38 L90 Line Current Differential System GE Multilin9.5 SINGLE-POLE TRIPPING 9 THEORY OF OPERATION9If none of the fault types indicated above is determined, then three-phase fault conditions are checked to detect the pres-ence of positive-sequence current and the absence of both zero-sequence and negative-sequence current. If these condi-tions are met, then the PHASE SELECT 3P FlexLogic™ operand is asserted; otherwise, the PHASE SELECT VOID operand isasserted, indicating that the phase selector failed to identify the fault type.Finally, the states of the following additional FlexLogic™ operands are determined.The phase selector operands are reset ½ cycle after the OPEN POLE OP FlexLogic™ operand is asserted or 500 ms afterthe disturbance detector (50DD) initially operated. In the reset state, all phase selector FlexLogic™ operands are reset untilreset conditions are removed and the phase selector is ready for the next operation.Figure 9–15: PHASE SELECTOR LOGIC9.5.3 COMMUNICATIONS CHANNELS FOR PILOT-AIDED SCHEMESa) DESCRIPTIONIn the L90 relay pilot-aided schemes transmit a code representing the type of fault determined by the local phase selectoraccording to the scheme logic. At a receiving terminal the local and remote data is combined to determine the action to beperformed. Schemes can be used with channels that can carry one, two or four bits. Using a one-bit channel, the schemesat all terminals of the line use their local phase selectors to identify the fault type and initiate appropriate tripping actions. InOPERAND DESCRIPTIONPHASE SELECT AG Asserted when a phase A to ground fault is detected.PHASE SELECT BG Asserted when a phase B to ground fault is detected.PHASE SELECT CG Asserted when a phase C to ground fault is detected.PHASE SELECT AB Asserted when a phase A to B fault is detected.PHASE SELECT BC Asserted when a phase B to C fault is detected.PHASE SELECT CA Asserted when a phase C to A fault is detected.PHASE SELECT ABG Asserted when a phase A to B to ground fault is detected.PHASE SELECT BCG Asserted when a phase B to C to ground fault is detected.PHASE SELECT CAG Asserted when a phase C to A to ground fault is detected.OPERAND DESCRIPTIONPHASE SELECT SLG Asserted if any of PHASE SELECT AG, PHASE SELECT BG, or PHASE SELECT CGoperands is active.PHASE SELECT MULTI-P Asserted if neither the PHASE SELECT SLG nor PHASE SELECT VOID operands are beingasserted.837027A5.CDRSRCn 50DD OPOPEN POLE OPSRCn VT FUSE FAIL OPDISTANCE SOURCE:ANDFLEXLOGIC OPERANDFLEXLOGIC OPERANDFLEXLOGIC OPERANDSETTINGDELAYDELAYI_1V_0V_1V_2I_0I_2FLEXLOGIC OPERANDSPHASE SELECT AGRESETSTARTPHASE SELECTORPHASE SELECT BGPHASE SELECT CGPHASE SELECT ABPHASE SELECT BCPHASE SELECT CAPHASE SELECT ABGPHASE SELECT BCGPHASE SELECT CAGPHASE SELECT 3PPHASE SELECT SLGPHASE SELECT MULTI-PPHASE SELECT VOID4 cycles500 ms00DELAY00.5 cycles
