Application - ABB RET670 Product Manual

ABB
Transformer protection RET670
Customized
Product version: 1.2

1. Application

RET670 provides fast and selective protection,
monitoring and control for two- and three-winding
transformers, autotransformers, generator-
transformer units, phase shifting transformers,
special railway transformers and shunt reactors.
The transformer IED is designed to operate
correctly over a wide frequency range in order to
accommodate power system frequency variations
during disturbances and generator start-up and
shut-down.
A very fast differential protection function with
settable CT ratio matching and vector group
compensation makes this IED the ideal solution
even for the most demanding applications. Since
RET670 has very low requirements on the main
CTs, no interposing CTs are required.It is suitable
for differential applications with multi-breaker
arrangements with up to six restraint CT inputs.
The differential protection function is provided
with 2nd harmonic and wave-block restraint
features to avoid tripping for magnetizing inrush
current, and 5th harmonic restraint to avoid
tripping for overexcitation.
The differential function offers a high sensitivity for
low-level internal faults. The unique and innovative
sensitive differential protection feature of the
RET670 provides the best possible coverage for
winding internal turn-to-turn faults, based on the
theory of symmetrical components .
A low impedance restricted earth-fault protection
function is available as a complimentary sensitive
and fast main protection against winding earth
faults. This function includes a directional zero-
sequence current criterion for additional security.
Additionally a high impedance differential function
is available. It can be used as restricted earth
fault or, as three functions are included, also as
differential protection on autotransformers, as
differential protection for a tertiary connected
reactor, as T-differential protection for the
transformer feeder in a mesh-corner or ring
arrangement, as tertiary bus protection and so on.
Tripping from pressure relief/Buchholz and
temperature devices can be done through the
transformer IED where pulsing, lock-out contact
output and so on, is performed. The binary inputs
are heavily stabilized against disturbance to
1MRK 504 117-BEN D
Issued: December 2012
prevent incorrect operations at for example dc
system capacitive discharges or DC earth faults.
The binary inputs are heavily stabilized against
disturbances to prevent incorrect operations
during for example during DC system capacitive
discharges or DC earth faults.
Distance protection functionality for phase-to-
phase and/or phase-to-earth faults is available as
back-up protection for faults within the
transformer and in the connected power system.
Versatile phase, earth, positive, negative and zero
sequence overcurrent functions, which can
optionally be made directional and/or voltage
controlled, provide further alternative backup
protection. Thermal overload with two time-
constants, volts per hertz, over/under voltage and
over/under frequency protection functions are
also available.
A built-in disturbance and event recorder provides
valuable data to the user about status and
operation for post-fault disturbance analysis.
Breaker failure protection for each transformer
breaker allows high speed back-up tripping of
surrounding breakers.
The transformer IED can also be provided with a
full control and interlocking functionality including
Synchrocheck function to allow integration of the
main and/or a local back-up control.
Out of Step function is available to separate
power system sections close to electrical centre
at occurring out of step.
The advanced logic capability, where user logic is
prepared with a graphical tool, allows special
applications such as automatic opening of
disconnectors in multi-breaker arrangements,
closing of breaker rings, load transfer logic and so
on. The graphical configuration tool ensures
simple and fast testing and commissioning.
Serial data communication is via optical
connections to ensure immunity against
disturbances.
The wide application flexibility makes this product
an excellent choice for both new installations and
the refurbishment of existing installations.
Revision: D
3