8.5.1 IdentificationGUID-E1720ADA-7F80-4F2C-82A1-EF2C9EF6A4B4 v1Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberFour step negative sequenceovercurrent protectionNS4PTOC I244 altIEC10000053 V1 EN-US46I28.5.2 Application GUID-343023F8-AFE3-41C2-8440-1779DD7F5621 v2Four step negative sequence overcurrent protection NS4PTOC (4612) is used inseveral applications in the power system. Some applications are:• Ground-fault and phase-phase short circuit protection of feeders in effectivelygrounded distribution and subtransmission systems. Normally these feeders haveradial structure.• Back-up ground-fault and phase-phase short circuit protection of transmissionlines.• Sensitive ground-fault protection of transmission lines. NS4PTOC (4612) canhave better sensitivity to detect resistive phase-to-ground-faults compared todistance protection.• Back-up ground-fault and phase-phase short circuit protection of powertransformers.• Ground-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 pickup levels and time delaysare needed. NS4PTOC (4612) can have up to four, individual settable steps. Theflexibility of each step of NS4PTOC (4612) function is great. The following optionsare possible:Non-directional/Directional function: In some applications the non-directionalfunctionality is used. This is mostly the case when no fault current can be fed from theprotected object itself. In order to achieve both selectivity and fast fault clearance, thedirectional function can be necessary. This can be the case for unsymmetrical faultprotection in meshed and effectively grounded transmission systems. The directionalnegative sequence overcurrent protection is also well suited to operate in teleprotectioncommunication schemes, which enables fast clearance of unsymmetrical faults ontransmission lines. The directional function uses the voltage polarizing quantity.Section 8 1MRK 511 401-UUS ACurrent protection184 Bay control REC670 2.2 ANSIApplication manual
