ABB 1MRK504053-BEN Application RET670 Transformer protection IED
Application
RET 670 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 automatic CT ratio matching and vector group compensation,
makes this IED the ideal solution even for the most demanding applications.
RET 670 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,
and 5th harmonic restraint to avoid tripping for overexcitation.
The differential function offers a high sensitivity for low-level internal faults.
RET 670’s unique and innovative sensitive differential protection feature, based on well-known theory of symmetrical components provide best possible coverage for
winding internal turn-to-turn faults.
A low impedance restricted earth-fault protection function is available as complimentary sensitive and fast main protection against winding earth
faults. This function includes a directional zero-sequence current criterion for additional security.
Alternatively 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 etc.
Tripping from Buchholz and temperature devices can be done through the IED where pulsing, lock-out etc. is performed.