RET670 1MRK002246-BD  Transformer protection RET670 ANSI

RET670 provides fast and selective protection, monitoring andcontrol for two-and three-winding transformers.
autotransformers, generator-transformer units, phase shiftingtransformers, special railway transformers and shunt reactorsThe transformer lED is designed to operate correctly over awide frequency range in order to accommodate power systemfrequency variations during disturbances and generator start-upand shut-down.
A very fast differential protection function with settable CT ratiomatching and phase shift compensation makes this lED theideal solution even for the most demanding applications. SinceRET670 has very low requirements on the main Cls, nointerposing CTs are required.lt is suitable for differentialapplications with multi-breaker arrangements with up to sixrestraint CT inputs. The differential protection function isprovided with 2nd harmonic and wave-block restraint featuresto avoid tripping for magnetizing inrush current, and 5thnarmonic restraint to avoid tripping for overexcitation.
The differential function offers a high sensitivity for low-levelinternal faults, The unique and innovative sensitive differentiaprotection feature of the RET670 provides the best possiblecoverage for winding internal turn-to-turn faults, based on thetheory of symmetrical components
A low impedance restricted ground-fault protection function isavailable as a complimentary sensitive and fast main protectionagainst winding ground faults. This function includes adirectional zero-sequence current criterion for additional
security
Additionally a hiah impedance differential function is available. ltcan be used as restricted ground fault or, as three functions areincluded, also as differential protection on autotransformers. asdifferential 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 devicescan be done through the transformer lED where pulsing, lock-out contact output and so on, is performed. The binary inputsare heavily stabilized against disturbance to prevent incorrectoperations at for example dc system capacitive discharges orDC ground faults.

RET670 1MRK004816-AC