7.6.7.5 DesignAt every execution of the function the following is calculated: active power P, reactivepower Q, rotor angle ROTORANG, quantity UCOSPHI, the positive-sequence currentCURRENT and voltage VOLTAGE. All other quantities, that can as well be read asoutputs, are only calculated if the Z(R, X) enters the limit of reach zone, which is acircle in the complex (R – X) plane. When the complex impedance Z(R, X) enters thelimit-of-reach region, the algorithm:• determines in which direction the impedance Z moves, that is, the direction thelens is traversed• measures the time taken to traverse the lens from one side to the other oneIf the traverse time is more than the limit 40 or 50 ms, a pole-slip is declared. If thecomplex impedance Z(R, X) exits the lens on the same side it entered, then it is a stablecase and the protected machine is still in synchronism. If a pole-slip has been detected,then it is determined in which zone the centre of oscillation is located. If the numberof actual pole-slips exceeds the maximum number of allowed pole-slips in either ofthe zones, a trip command is issued taking care of the circuit breaker safety.IEC10000116-3-en.vsdGENMODECalculation ofR and X partsof the complexpositive-sequenceimpedanceZ(R, X)UPSREUPSIMUPSMAGRIPSREIPSIMZ(R,X)Z(R,X)within limit ofreach?XNOReturnYESZ(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 2OpencircuitbreakersafelyTRIPTRIPZ1TRIPZ2UCOSPHIUCOSPHIROTORANGSLIPFREQGENMODEMOTMODENOCalculation ofR and X partsof the complexpositive-sequenceimpedanceZ(R, X)UPSREUPSIMUPSMAGRIPSREIPSIMZ(R,X)Z(R,X)within limit ofreach?XNOReturnYESZ(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 2OpencircuitbreakersafelyTRIPTRIPZ1TRIPZ2UCOSPHIUCOSPHIROTORANGSLIPFREQMOTMODENOIEC10000116 V3 ENFigure 118: OOSPPAM Simplified function block1MRK502052-UEN B Section 7Impedance protection271Technical manual
