I m in M A X IfA IfB IM, ,( )³EQUATION287 V1 EN-US (Equation 36)Where:IfA and IfB have been described for the single line case.Considering the safety margins mentioned previously, the minimum setting (Is) is:Is = 1.3 × IminEQUATION288 V3 EN-US (Equation 37)Transformer inrush current shall be considered.The setting of the protection is set as a percentage of the base current (IBase).Operation: set the protection toOn orOff.IN>>: Set operate current in % ofIBase.StValMult: The operate current can be changed by activation of the binary input ENMULT tothe set factorStValMult.7.4 Four step residual overcurrent protection, (Zerosequence or negative sequence directionality)EF4PTOC IP14509-1 v67.4.1 IdentificationM14881-1 v5Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberFour step residual overcurrentprotectionEF4PTOC 4(IN>)4 alt4TEF-REVA V2 EN-US51N_67N7.4.2 Application M12509-12 v9The four step residual overcurrent protection EF4PTOC is used in several applications in thepower system. Some applications are:• Earth-fault protection of feeders in effectively earthed distribution and subtransmissionsystems. Normally these feeders have radial structure.• Back-up earth-fault protection of transmission lines.• Sensitive earth-fault protection of transmission lines. EF4PTOC can have better sensitivityto detect resistive phase-to-earth-faults compared to distance protection.• Back-up earth-fault protection of power transformers.• Earth-fault protection of different kinds of equipment connected to the power systemsuch as shunt capacitor banks, shunt reactors and others.1MRK 511 358-UEN A Section 7Current protection117Application manual
