available. For the complete list of available inverse curves please refer to section"Inverse time characteristics".• Time delay related settings. By these parameter settings the properties like definitetime delay, minimum operating time for inverse curves and reset time delay aredefined.• Supervision by second harmonic blocking feature (Enabled/Disabled). By thisparameter setting it is possible to prevent operation of the step if the second harmoniccontent in the residual current exceeds the preset level.Simplified logic diagram for one residual overcurrent step is shown in figure 99.aba>bInverseOR|IOP|PU_STxTRSTxANDHarmRestrainx=DisabledPickupxBLKxBLOCKOR2ndH_BLOCK_Int Characteristn=InverseCharacteristn=DefTimeDirModeSelx=DisabledDirModeSelx=Non-directionalDirModeSelx=ForwardDirModeSelx=ReverseANDANDFORWARD_IntREVERSE_IntOROR STEPx_DIR_IntANSI09000638-3-en.vsd00-txAND00-txMinANDANSI09000638 V3 ENFigure 99: Simplified logic diagram for residual overcurrentThe protection can be completely blocked from the binary input BLOCK. Output signalsfor respective step, PU_STx and TRSTx and , can be blocked from the binary inputBLKn.7.6.7.7 Directional supervision element with integrated directional comparisonfunctionIt shall be noted that at least one of the four residual overcurrent steps shallbe set as directional in order to enable execution of the directionalsupervision element and the integrated directional comparison function.The protection has integrated directional feature. The operating quantity current I3PDIRis always used. The polarizinwcg method is determined by the parameter settingSection 7 1MRK 506 335-UUS ACurrent protection226Technical manual
