ABB RELION 670 Series Applications Manual page 161

1MRK 505 337-UUS A
7.2 Four step single phase overcurrent protection
PH4SPTOC (51)
7.2.1 Identification
Function description
Four step single phase overcurrent
protection
7.2.2 Application
The Four step single phase overcurrent protection(PH4SPTOC, 51) function 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.
The single phase overcurrent protection is used in IEDs having only input from one phase, for
example busbar protection for large busbars (with many bays).
In many applications several steps with different current pick up levels and time delays are
needed. PH4SPTOC(51) can have up to four different, individual settable, steps. The flexibility of
each step of PH4SPTOC(51) function is great. The following options are possible:
Choice of delay time 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 all overcurrent
IEDs, to be co-ordinated against each other, should have the same time delay characteristic.
Therefore a wide range of standardised inverse time characteristics are available: IEC and ANSI. It
is also possible to programme a user defined inverse time characteristic.
Normally it is required that the phase overcurrent function shall reset as fast as possible when the
current level gets lower than the operation level. In some cases some sort of time delayed reset is
required. Therefore three different kinds of reset time 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 then the rated current of the
Application manual
IEC 61850 IEC 60617
identification identification
PH4SPTOC
I>
4
alt
4
OC V1 EN-US
Current protection
ANSI/IEEE C37.2
device number
51
Section 7
SEMOD127812-1 v2
SEMOD127810-2 v2
SEMOD127937-4 v2
155