ABB RELION 670 Series Applications Manual page 151

1MRK 505 337-UUS A
Section 7
7.1 Four step phase overcurrent protection
OC4PTOC(51/67)
7.1.1 Identification
Function description
Four step phase overcurrent
protection 3-phase output
7.1.2 Application
The Four step phase overcurrent protection 3-phase output OC4PTOC (51_67) is used in several
applications in the power system. Some applications are:
• Short circuit protection of feeders in distribution and subtransmission systems. Normally
these feeders have 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 power system 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 pick up levels and time delays are
needed. OC4PTOC (51_67) can have up to four different, individual settable, steps.The flexibility of
each step of OC4PTOC (51_67) is great. The following options are possible:
Non-directional / Directional function: In most applications the non-directional functionality is
used. This is mostly the case when no fault current can be fed from the protected object itself. In
order to achieve both selectivity and fast fault clearance, the directional function can be
necessary.
Choice of delay time characteristics: There are several types of delay time characteristics available
such as definite time delay and different types of inverse time delay characteristics. The selectivity
between different overcurrent protections is normally enabled by co-ordination between the
Application manual
Current protection
IEC 61850
identification
OC4PTOC
If VT inputs are not available or not connected, setting parameter
step 1, 2, 3 or 4) shall be left to default value
IEC 60617 ANSI/IEEE C37.2
identification device number
51_67
TOC-REVA V2 EN-US
Non-directional .
Section 7
Current protection
SEMOD129998-1 v7
M14885-1 v5
M15335-3 v8
DirModeSelx ( x =
145