m1.3.Is inI ³EQUATION288 V2 EN (Equation 119)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 to Enabled or Disabled.Pickup: Set operate current in % of IBase. IBase is a global parameter valid for allfunctions in the IED.7.6 Four step residual overcurrent protection, zero,negative sequence direction EF4PTOC (51N/67N)7.6.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberFour step residual overcurrentprotection, zero or negative sequencedirectionEF4PTOC2IEC11000263 V1 EN51N/67N7.6.2 ApplicationThe four step residual overcurrent protection, zero or negative sequence directionEF4PTOC (51N_67N) is used in several applications in the power system. Someapplications are:• Ground-fault protection of feeders in effectively grounded distribution systems.Normally these feeders have radial structure.• Back-up ground-fault protection of subtransmission and transmission lines.• Sensitive ground-fault protection of transmission lines. EF4PTOC (51N_67N) canhave better sensitivity to detect resistive phase-to-ground-faults compared to distanceprotection.• Back-up ground-fault protection of power transformers with ground source atsubstation.Section 7 1MRK 506 334-UUS ACurrent protection202Application manual
