7.2 Directional phase overcurrent protection, four stepsOC4PTOC SEMOD129998-1 v87.2.1 IdentificationM14885-1 v6Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberDirectional phase overcurrentprotection, four stepsOC4PTOCTOC-REVA V2 EN-US51_677.2.2 Application M15335-3 v9Directional phase overcurrent protection, four steps OC4PTOC is used in severalapplications in the power system. Some applications are:• Short circuit protection of feeders in distribution and subtransmission systems.Normally these feeders have a radial structure.• Back-up short circuit protection of transmission lines.• Back-up short circuit protection of power transformers.• Short circuit protection of different kinds of equipment connected to the powersystem such as; shunt capacitor banks, shunt reactors, motors and others.• Back-up short circuit protection of power generators.In many applications several steps with different current pickup levels and timedelays are needed. OC4PTOC can have up to four different, individually settablesteps. The following options are possible:Non-directional / Directional function: In most 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 faultclearance, the directional function can be necessary.If VT inputs are not available or not connected, the settingparameter DirModex (x = step 1, 2, 3 or 4) shall be left to thedefault value Non-directional.Choice of time delay characteristics: There are several types of time delaycharacteristics available such as definite time delay and different types of inversetime delay characteristics. The selectivity between different overcurrent protectionsis normally enabled by co-ordination between the function time delays of thedifferent protections. To enable optimal co-ordination between all overcurrentSection 7 1MRK 504 169-UEN ACurrent protection106 Transformer protection RET650 2.2 IECApplication manual
