Adaptive frequency tracking is included to ensure proper operation of the generatordifferential protection during varying frequency conditions.An open CT circuit condition creates unexpected operations for Generator differentialprotection under the normal load conditions. It is also possible to damage secondaryequipment due to high voltage produced from open CT circuit outputs. Therefore, it maybe a requirement from security and reliability points of view to have open CT detectionfunction to block Generator differential protection function in case of open CT conditionsand at the same time produce the alarm signal to the operational personal to make quickremedy actions to correct the open CT condition.Generator differential protection GENPDIF (87G) is also well suited to generate fast,sensitive and selective fault clearance, if used to protect shunt reactors or small busduct.6.4.3 Function blockGENPDIF (87G)I3PNCT*I3PTCT*BLOCKBLKRESBLKUNRESBLKNSUNRBLKNSSENDESENSITTRIPTRIPRESTRIPUNRETRNSUNRTRNSSENSPICKUPBLKHOPENCTOPENCTALIDMAG_AIDMAG_BIDMAG_CIDMAG_NSIBIASANSI07000025-2-en.vsdANSI07000025 V3 ENFigure 49: GENPDIF (87G) function block6.4.4 SignalsTable 44:GENPDIF (87G) Input signalsName Type Default DescriptionI3PNCT GROUPSIGNAL- Neutral side CT inputI3PTCT GROUPSIGNAL- Terminal side CT inputBLOCK BOOLEAN 0 Block of functionBLKRES BOOLEAN 0 Block of trip from the restrained diff. protectionBLKUNRES BOOLEAN 0 Block of trip from unrestrained diff. prot.Table continues on next page1MRK 502 048-UUS A Section 6Differential protection133Technical manual
