1. Application
RET670 provides fast and selective protection,
monitoring and control for two- and three-winding
transformers, autotransformers, generator-
transformer units 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
automatic CT ratio matching and phase shift
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 well-
known theory of symmetrical components .
Low impedance restricted ground-fault protection
functions are available as complimentary sensitive
and fast main protection against winding ground
faults. This function includes a directional zero-
sequence current criterion for additional security.
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 prevent
incorrect operations at for example, dc system
capacitive discharges or DC ground faults.
Distance protection functionality for phase-to-phase
and/or phase-to-ground faults is available as back-
up protection for faults within the transformer and in
the connected power system.
Versatile phase, ground, positive 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.
Transformer protection RET670 ANSI 1MRK 504 118-BUS A
Pre-configured
Product version: 1.2 Issued: May 2012
Revision: A
ABB 3
