ABB Relion 670 Series Applications Manual page 137

1MRK 511 401-UEN Rev. K
8.2 Directional phase overcurrent protection, four steps
OC4PTOC
8.2.1 Identification
Function description
Directional phase overcurrent
protection, four steps
8.2.2 Application
Directional phase overcurrent protection, four steps OC4PTOC 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 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 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 pickup levels and time delays are
needed. OC4PTOC can have up to four different, individually settable steps. 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 time delay characteristics: There are several types of time delay 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 for 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 motor. Therefore, there is a possibility to give a setting of a multiplication factor
Bay control REC670
Application manual
IEC 61850
identification
OC4PTOC
If VT inputs are not available or not connected, the setting parameter
x = step 1, 2, 3 or 4) shall be left to the default value Non-directional .
(
© Copyright 2017 Hitachi Power Grids. All rights reserved
IEC 60617 ANSI/IEEE C37.2
identification device number
51_67
TOC-REVA V2 EN-US
Section 8
Current protection
SEMOD129998-1 v8
M14885-1 v6
M15335-3 v9
DirModex
131