ABB RET670 1MRK004816-AC Protective devices

Description

RET670 provides fast and selective protection, monitoring andcontrol for two- and three-winding transformers,autotransformers, step-up transformers and generatortransformer block units, phase shifting transformers, specialrailway transformers and shunt reactors. The IED is designed tooperate correctly over a wide frequency range in order toaccommodate power system frequency variations duringdisturbances and generator start-up and shut-down.RET670 has a fast, low-impedance differential protectionfunction with very low requirements on the CTs.It is suitable fordifferential applications with multi-breaker arrangements withup to six restraint CT inputs. The differential protection functionis provided with a 2nd harmonic and waveform-block restraintfeature to avoid tripping for CT saturation and transformerinrush current, and 5th harmonic restraint to avoid tripping fortransformer overexcitation.The differential function offers a high sensitivity for low-levelinternal faults by using a sensitive differential protection featurebased on an amplitude measurement and directionalcomparison of the negative sequence components.Multiple low impedance restricted earth-fault protectionfunctions are available as a sensitive and fast main protectionagainst winding earth faults. This function includes a internal/external fault discriminator for additional security.Additionally, a high impedance differential protection function isavailable. It can be used for different applications includingrestricted earth fault protection as winding protection,autotransformer differential protection, shunt reactorprotection, T-feeder protection, busbar protection andgenerator differential protection.