0.8 loadRFPEZx Z EQUATION792 V2 EN-US (Equation 218)This equation is applicable only when the loop characteristic angle for the singlephase-to-earth faults is more than three times as large as the maximum expectedload-impedance angle. More accurate calculations are necessary according to theequation below:min2 1 00.8 cos sin2 1 0loadR Zx R ZxRFPEZx Z X Zx X Zx EQUATION578 V5 EN-US (Equation 219)Where:ϑ is a maximum load-impedance angle, related to the minimum load impedance conditions.All this is applicable for all measuring zones when no power swing detectionelement is in the protection scheme. Use an additional safety margin ofapproximately 20% in cases when a power swing detection element is in theprotection scheme, refer to the description of the power swing detection(ZMRPSB) function.8.5.3.8 Load impedance limitation, with load encroachment functionactivated SEMOD154704-129 v1The parameters for load encroachment shaping of the characteristic are found in thedescription of the phase selection with load encroachment function, section"Resistive reach with load encroachment characteristic". If the characteristic for theimpedance measurement shall be shaped with the load encroachment algorithm, theparameter OperationLdCmp in the phase selection has to be switched On.8.5.3.9 Setting of minimum operating currents SEMOD154704-132 v2The operation of the distance function will be blocked if the magnitude of thecurrents is below the set value of the parameter IMinOpPE.The default setting of IMinOpPE is 20% of IBase where IBase is the chosen basecurrent for the analog input channels. The value have been proven in practice to besuitable in most of the applications. However, there might be applications where itis necessary to increase the sensitivity by reducing the minimum operating currentdown to 10% of the IED base current. This happens especially in cases, when theIED serves as a remote back-up protection on series of very long transmissionlines.If the load current compensation is activated, there is an additional criteriaIMinOpIN that will block the phase-earth loop if the 3I0<IMinOpIN. The defaultsetting of IMinOpIN is 5% of the IED base current IBase.1MRK 506 369-UEN B Section 8Impedance protectionLine distance protection REL670 2.2 IEC 281Application manual
