6.4.8 Second harmonic blocking elementA harmonic restrain of the Four step residual overcurrent protection function EF4PTOC51N_67N can be chosen. If the ratio of the 2nd harmonic component in relation to thefundamental frequency component in the residual current exceeds the pre-set leveldefined by parameter setting 2ndHarmStab. Any of the four residual overcurrent stagescan be selectively blocked by parameter setting HarmRestrainx. When 2nd harmonicrestraint feature is active the EF4PTOC 51N_67N function output signal 2NDHARMDwill be set to logical value one.aba>bBLOCKANDIOPExtract secondharmonic currentcomponentExtractfundamentalcurrent component X2ndHarmStababa>baba>b0.07*IBaseIEC13000015-1-en.vsd2NDHARMDUseStartValueIN1>IN2>IN3>IN4>aba>b|IOP|tt=70ms OR ANDBlkParTransf=Onq-1OR 2ndH_BLOCK_IntIEC13000015 V1 ENFigure 42: Second harmonic blockingSection 6 1MRK 511 287-UUS ACurrent protection114Technical manual
