Section 2 Application2.1 General IED applicationGUID-EB939A4F-1C88-4EB1-A217-571FEF72AC7B v4The RET650 provides fast and selective protection, monitoring and controlfunctions for two- and three-winding transformers, autotransformers, generator-transformer units and shunt reactors. The IED is designed to operate correctly overa wide frequency range in order to accommodate power system frequencyvariations during disturbances and generator startup and shutdown. Apparatuscontrol for 3 circuit breakers is included.A fast differential protection function with built-in transformer ratio matching andvector group compensation makes this IED the ideal solution even for the mostdemanding applications. Since RET650 has very low requirements on the mainCTs, no interposing CTs are required. The differential protection function isprovided with 2nd harmonic and waveform-blocking restraint features to avoidtripping for magnetizing inrush current, and 5th harmonic restraint to avoidtripping for overexcitation.The differential function offers a high sensitivity for low-level internal faults. Theunique and innovative sensitive differential protection feature of the RET650provides the best possible coverage for internal turn-to-turn winding faults, basedon the theory of symmetrical components.A low impedance restricted earth-fault protection function is available as acomplimentary sensitive and fast main protection against winding earth faults. Thisfunction includes a directional zero-sequence current criterion for additionalsecurity.Tripping from pressure relief/Buchholz and temperature devices can beimplemented through the IED's binary inputs, where trip signal conditioning can beperformed (pulsing, lockout, additional logics, etc.). The binary inputs arethoroughly stabilized against disturbances in order to prevent incorrect operationsdue to DC system capacitive discharges or DC earth faults, for example.Versatile phase, earth and zero sequence overcurrent functions with directionalcapability provide further alternative backup protections. Thermal overload withtwo time-constants and breaker failure protection is also available.A built-in disturbance and event recorder provides valuable data to the user aboutstatus and operation for post-fault disturbance analysis.Two pre-configured packages have been defined for the following applications:1MRK 504 169-UEN A Section 2ApplicationTransformer protection RET650 2.2 IEC 23Application manual
