Identification; Application - ABB Relion 670 Series Applications Manual

Section 7
Current protection
7.2.1

Identification

Function description
Four step phase overcurrent
protection 3-phase output
7.2.2

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
function time delays of the different protections. To enable optimal co-ordination between all
overcurrent protections, they should have the same time delay characteristic. Therefore a wide
range of standardized inverse time characteristics are available: IEC and ANSI. It is also possible to
tailor make the inverse time characteristic.
Normally it is required that the phase overcurrent protection shall reset as fast as possible when
the current level gets lower than the operation level. In some cases some sort of delayed reset is
required. Therefore different kinds of reset characteristics can be used.
For some protection applications there can be a need to change the current pick-up level for some
time. A typical case is when the protection will measure the current to a large motor. At the start
up sequence of a motor the start current can be significantly larger than the rated current of the
124
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 .
1MRK 511 358-UUS A
M14885-1 v5
M15335-3 v8
DirModeSelx ( x =
Application manual