6.3.6.5 DesignWhen the complex impedance Z(R, X) enters the limit-of-reach region, thealgorithm determines the direction impedance Z moves, that is, the direction thelens is traversed and measures the time taken to traverse the lens from one side tothe other. If the traverse time is more than the limit 40 or 50 ms, a pole-slip isdeclared. If the complex impedance Z(R, X) exits the lens on the same side itentered, then it is a stable case and the protected machine is still in synchronism. Ifa pole-slip has been detected, then it is determined in which zone the centre ofoscillation is located. If the number of actual pole-slips exceeds the maximumnumber of allowed pole-slips in either of the zones, a trip command is issuedtaking care of the circuit breaker safety.IEC10000116-1-en.vsdCalculation ofR and X partsof the complexpositive-sequenceimpedanceZ(R, X)UPSREUPSIMUPSMAGRIPSREIPSIMZ(R,X)Z(R,X)within limit ofreach?XNO ReturnYESZ(R,X)within lenscharacteristic?NOYESZ(R,X)entered lensfrom?Function alertRIGHTLEFT Z(R,X)exited lenson the left-handside?NOYESYES (pole-slip!)Wastraverse timemore than50 ms?Motor losingstep ?Generator losingstep ?NOXRCalculation ofpositive-sequenceactive power P,reactive power Q,rotor angleROTORANGandUCOSPHIPQROTORANG>= 1Numberof pole-slipsexceeded ina zone?ZONE 1ZONE 2OpencircuitbreakersafelyTRIPTRIPZ1TRIPZ2UCOSPHIPQUCOSPHIROTORANGSLIPFREQGEBMODEMOTMODENOCalculation ofR and X partsof the complexpositive-sequenceimpedanceZ(R, X)UPSREUPSIMUPSMAGRIPSREIPSIMZ(R,X)Z(R,X)within limit ofreach?XNO ReturnYESZ(R,X)within lenscharacteristic?NOYESZ(R,X)entered lensfrom?Function alertRIGHTLEFT Z(R,X)exited lenson the left-handside?NOYESYES (pole-slip!)Wastraverse timemore than50 ms?Motor losingstep ?Generator losingstep ?NOXRCalculation ofpositive-sequenceactive power P,reactive power Q,rotor angleROTORANGandUCOSPHIPQROTORANG>= 1Numberof pole-slipsexceeded ina zone?ZONE 1ZONE 2OpencircuitbreakersafelyTRIPTRIPZ1TRIPZ2UCOSPHIPQUCOSPHIROTORANGSLIPFREQGEBMODEMOTMODENOIEC10000116 V1 ENFigure 76: OOSPPAM Simplified function blockSection 6 1MRK 502 034-UEN -Impedance protection140Technical Manual
