accidental event be given precaution, the phase-to-earth reach (RFPEZx) of allinstantaneous zones has to be set below the emergency load for the pole-opensituation. Again, this is only for the application where there is a risk that onebreaker pole would open without a preceding fault. If this never happens, forexample when there is no parallel circuit, there is no need to change any phase-to-earth reach according to the pole-open scenario.7.1.3.9 Other settings GUID-9D65B411-6FE2-433B-AE6C-C6DD716D1181 v7IMinOpPEZx and IMinOpPPZxThe ability for a specific loop and zone to issue a start or a trip is inhibited if themagnitude of the input current for this loop falls below the threshold value definedby these settings. The output of a phase-to-earth loop Ln is blocked if ILn <IminOpPE(Zx). In is the RMS value of the fundamental current in phase n.The output of a phase-to-phase loop LmLn is blocked if ILmLn < IMinOpPP(Zx).ILmLn is the RMS value of the vector difference between phase currents Lm andLn.Both current limits IMinOpPEZx and IMinOpPPZx are automatically reduced to75% of regular set values if the zone is set to operate in reverse direction, that is,OperationDir is set to Reverse.OpModePPZx and OpModePEZxThese settings, two per zone (x=1,2..5&RV), with options {Off, Quadrilateral,Mho, Offset}, are used to set the operation and characteristic for phase-to-earth andphase-to-phase faults, respectively.For example, in one zone it is possible to choose Mho characteristic for the threePh-Ph measuring loops and Quadrilateral characteristic for the three Ph-Emeasuring loops.DirModeZxThis setting defines the operating direction for zones Z3, Z4 and Z5 (thedirectionality of zones Z1, Z2 and ZRV is fixed). The options are Non-directional,Forward or Reverse. The result from respective set value is illustrated in figure64,where the positive impedance corresponds to the direction out on the protectedline.Section 7 1MRK 505 393-UEN BImpedance protection130 Line differential protection RED650 2.2 IECApplication manual
