Section 3 Ied Application; General Ied Application - ABB RET670 Applications Manual

1MRK504116-UUS C
Section 3
3.1
Application manual
IED application
About this chapter
This chapter describes the use of the included software functions in the IED. The
chapter discusses application possibilities and gives guidelines for calculating settings
for a particular application.

General IED 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 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 the theory
of symmetrical components .
A low impedance restricted ground-fault protection function is available as a
complimentary sensitive and fast main protection against winding ground 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 ground 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.
Section 3
IED application
31