tPRCrvx, tTRCrvx, tCRCrvx: Parameters for user programmable of inverse resettime characteristic curve. Further description can be found in the technicalreference manual.8.3 Four step directional negative phase sequenceovercurrent protection NS4PTOC GUID-E8CF8AA2-AF54-4FD1-A379-3E55DCA2FA3A v18.3.1 IdentificationGUID-E1720ADA-7F80-4F2C-82A1-EF2C9EF6A4B4 v1Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberFour step negative sequenceovercurrent protectionNS4PTOC I244 altIEC10000053 V1 EN-US46I28.3.2 Application GUID-343023F8-AFE3-41C2-8440-1779DD7F5621 v2Four step negative sequence overcurrent protection NS4PTOC is used in severalapplications in the power system. Some applications are:• Earth-fault and phase-phase short circuit protection of feeders in effectivelyearthed distribution and subtransmission systems. Normally these feeders haveradial structure.• Back-up earth-fault and phase-phase short circuit protection of transmissionlines.• Sensitive earth-fault protection of transmission lines. NS4PTOC can havebetter sensitivity to detect resistive phase-to-earth-faults compared to distanceprotection.• Back-up earth-fault and phase-phase short circuit protection of powertransformers.• Earth-fault and phase-phase short circuit protection of different kinds ofequipment connected to the power system such as shunt capacitor banks, shuntreactors and others.In many applications several steps with different current operating levels and timedelays are needed. NS4PTOC can have up to four, individual settable steps. Theflexibility of each step of NS4PTOC function is great. The following options arepossible:Non-directional/Directional function: In some applications the non-directionalfunctionality is used. This is mostly the case when no fault current can be fed fromthe protected object itself. In order to achieve both selectivity and fast fault1MRK 511 407-UEN C Section 8Current protectionPhasor measurement unit RES670 2.2 IEC 141Application manual
