2 X1PE + X0arctan 2 R1PE + R0loopj é ù×ê ú= ×ê úë ûEQUATION1457 V1 EN-US (Equation 84)Setting of the resistive reach for the underreaching zone1 must follow thefollowing condition:4.5 1RFPE X£ ×EQUATION569 V2 EN-US (Equation 85)The fault resistance for phase-to-phase faults is normally quite low, compared tothe fault resistance for phase-to-earth faults. Limit the setting of the zone1 reach inresistive direction for phase-to-phase loop measurement to:3 1RFPP X£ ×EQUATION570 V2 EN-US (Equation 86)8.1.3.8 Load impedance limitation, without load encroachment functionSEMOD168247-91 v3The following instructions is valid when the load encroachment function is notactivated, which is done by setting the parameter Rld for the Phase Selector to itsupper limit. If the load encroachment function is to be used for all or some of themeasuring zones, the load limitation for those zones according to this chapter canbe omitted. Check the maximum permissible resistive reach for any zone to ensurethat there is a sufficient setting margin between the IED boundary and theminimum load impedance. The minimum load impedance (Ω/phase) is calculatedas:ZloadminU2S-------=EQUATION571 V1 EN-US (Equation 87)Where:U is the minimum phase-to-phase voltage in kVS is the maximum apparent power in MVA.The load impedance [Ω/phase] is a function of the minimum operation voltage andthe maximum load current:ZloadUmin3 Imax×----------------------=EQUATION574 V1 EN-US (Equation 88)1MRK 506 369-UEN B Section 8Impedance protectionLine distance protection REL670 2.2 IEC 199Application manual
