This setting opens an opportunity to enable phase-to-earth measurement for phase-to-phase-earth faults. It determines the level of residual current (3I0) above whichphase-to-earth measurement is activated (and phase-to-phase measurement isblocked). The relations are defined with the equation.0 maxRe3 100 phIN leasePEI I× ³ ×EQUATION2548 V1 EN-US (Equation 75)Where:INReleasePE the setting for the minimum residual current needed to enable operation in thephase-to-earth fault loops in %Iphmax the maximum phase current in any of the three phasesBy default, this setting is set excessively high to always enable phase-to-phasemeasurement for phase-to-phase-earth faults. This default setting value must bemaintained unless there are very specific reasons to enable phase-to-earthmeasurement. Even with the default setting value, phase-to-earth measurement isactivated whenever appropriate, like in the case of simultaneous faults: two earthfaults at the same time, one each on the two circuits of a double line.One specific situation where the INReleasePE setting should be altered is for cross-country faults in high impedance earthed networks, in order to make sure thatoperation is phase-to-earth. This is particularly important when using phasepreference logic, since it is only working per phase, not for phase-to-phasemeasurement. The limit should be set so that it will be exceeded during a cross-country fault.7.1.3.10 ZMMMXU settings GUID-42F340C5-93CC-40AE-B67D-DC1B7D0520DA v1ZZeroDbMinimum level of impedance in % of range (ZMax-ZMin) used as indication ofzero impedance (zero point clamping). Measured values below ZZeroDb are forcedto zero.ZHiHiLim, ZHiLim, ZLowLim and ZLowLowLimAll measured values are supervised against these four settable limits. It providesthe attribute "range" in the data class MV (measured value) with the typeENUMERATED (normal, high, low, high-high and low-low) inZMFPDIS.ZMMMXU.ZLimHysHysteresis value in % of range (ZMax-ZMin), common for all limits. It is used toavoid the frequent update of the value for the attribute “range”.1MRK 505 393-UEN B Section 7Impedance protectionLine differential protection RED650 2.2 IEC 133Application manual
