ABB Relion REL650 Series Product Manual page 23

Line distance protection REL650
Version 2.2
consequence of this the risk of internal phase-to-phase or
phase-to-earth faults will increase.
The thermal overload protection (TRPTTR) estimates the
internal heat content of the transformer (temperature)
continuously. This estimation is made by using a thermal
model of the transformer with two time constants, which is
based on current measurement.
Two warning levels are available. This enables actions in
the power system to be done before dangerous
temperatures are reached. If the temperature continues to
increase to the trip value, the protection initiates a trip of the
protected transformer.
The estimated time to trip before operation is presented.
Breaker failure protection CCRBRF, 3-phase
activation and output
Breaker failure protection, 3-phase activation and output
(CCRBRF) ensures fast backup tripping of surrounding
breakers in case the own breaker fails to open. CCRBRF
can be current based, contact based, or an adaptive
combination of these two conditions.
A current based check with extremely short reset time is
used as check criterion to achieve high security against
inadvertent operation.
Breaker failure protection, 3-phase activation and output
(CCRBRF) current criteria can be fulfilled by one or two
phase currents the residual current, or one phase current
plus residual current. When those currents exceed the user
defined settings, the function is triggered. These conditions
increase the security of the backup trip command.
CCRBRF function can be programmed to give a three-
phase retrip of the own breaker to avoid inadvertent tripping
of surrounding breakers.
Stub protection STBPTOC
When a power line is taken out of service for maintenance
and the line disconnector is opened the voltage
transformers will mostly be outside on the disconnected
part. The primary line distance protection will thus not be
able to operate and must be blocked.
The stub protection (STBPTOC) covers the zone between
the current transformers and the open disconnector. The
three-phase instantaneous overcurrent function is released
from a normally closed, NC (b) auxiliary contact on the line
disconnector.
Overcurrent protection with binary release BRPTOC
Overcurrent protection with binary release (BRPTOC) is a
simple, non-directional three-phase overcurrent protection
function with definite time delay. A single step is available
within the function. The current pickup level and definite
time delay can be set independently. It is possible to
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release the function operation via a binary signal. If the
binary signal is not connected, the function will
automatically operate in a continuous mode of operation.
Several function instances are available.
From the measured three-phase currents, various types of
measurement modes such as DFT, Peak, and Peak-to-peak
can be selected for the BRPTOC operation.
Peak and Peak-to-Peak measurement mode allow this
function to be used as instantaneous over-current protection
as well. If required by application, short time delay can also
be applied.
BRPTOC can be used for different line and transformer
protection applications. If required, it can also be used to
supervise on-load tap-changer operation.
Pole discordance protection CCPDSC
Circuit breakers and disconnectors can end up with the
phases in different positions (close-open), due to electrical
or mechanical failures. An open phase can cause negative
and zero sequence currents which cause thermal stress on
rotating machines and can cause unwanted operation of
zero sequence or negative sequence current functions.
Normally the own breaker is tripped to correct such a
situation. If the situation persists the surrounding breakers
should be tripped to clear the unsymmetrical load situation.
The pole discordance function operates based on
information from the circuit breaker logic with additional
criteria from phase selective current unsymmetry.
Broken conductor check BRCPTOC
The main purpose of the function Broken conductor check
(BRCPTOC) is the detection of broken conductors on
protected power lines and cables (series faults). Detection
can be used to give alarm only or trip the line breaker.
Voltage-restrained time overcurrent protection
VRPVOC
Voltage-restrained time overcurrent protection (VRPVOC)
function is recommended as a backup protection for
generators.
Voltage-restrained time overcurrent protection (VRPVOC)
function can be used as generator backup protection
against short-circuits.
The overcurrent protection feature has a settable current
level that can be used either with definite time or inverse
time characteristic. Additionally, it can be voltage controlled/
restrained.
One undervoltage step with definite time characteristic is
also available within the function in order to provide
functionality for overcurrent protection with undervoltage
seal-in.
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