Description
Features
•Pre-configured and ready to use •Easily adapted to different substationconfigurations •Real-time clock with external synchronization •Extensive self-supervision •Built-in local HMI with LED indications •No interposing CTs are required •No switching in CT secondary circuits is needed •Low CT requirements, only 2 ms to saturationneeded for correct operation •Different CT ratios can be used in all bays •Stability is ensured for through faults, even withheavy CT saturation and maximum remanencein the CT core •One three-phase terminal with one measuringzone provides busbar protection for a singlezone with up to six bays •Three one-phase terminals with two measuringzones for up to 18 CT inputs provide phasesegregated busbar protection for largersubstations •Single one-phase terminal with two measuringzones can be used together with up to 18auxiliary summation CTs for cost-efficientbusbar protection
Protection functions •Differential protection with operating timetypically 10-15 ms •Open CT detection function •Load transfer function Monitoring •Event list with up to 16 events •Display of analog service values for each phaseand zone of protection Hardware •19” rack case size •One or two analog input modules •Current inputs for 1A or 5A main CTs by tapconnection •Power supply modules covering 24 V to 250 VDC ± 20% •Binary output module with 24 outputs(pre-configured at the factory) •Binary input module with 16 inputs(pre-configured at the factory) •Optional test switch module
The numerical Differential Protection Terminal RED 521 providesfast and selective phase-segregated protection for busbars, aswell as generators, autotransformers, shut reactors and capacitorbanks. The superior security and dependability of this terminalis based on ABB’s deep knowledge of busbar protection.As an option, RED 521 offers a more cost-efficient solution usingthe summation CT principle.
The RED 521 terminal is more than just a first-class product.It is supplied with a value-adding information package about theproduct and its use in your application. Information such astechnical data, user documentation and connection diagrams isessential to ensure the smooth and efficient use of the terminalthroughout its lifetime. You can access this information easily viathe operator ’s workplace or from your PC with InformIT AspectObject Viewer freeware.
The extremely short operate time of RED 521 is typically 10-15ms at all internal faults, regardless of the number of connectedfeeders. At the same time, the terminal maintains completestability for external faults, even when heavy CT saturationoccurs. This unique combination of speed and stability is essentialfor effective busbar protection. RED 521 has very low CTrequirements compared to other numerical differential protectiondevices due to its unique measuring principle. This also allowssharing of CT circuits with other relays to save costs. The lowCT requirements guarantee stability and correct operation aslong as the CT is not saturated for at least two millisecondsduring each power system cycle.
RED 521 also provides superior sensitivity for internal faults,thus protecting your power system objects from extensivedamage and long repair times. The terminal is capable of effectivelyrecognizing and operating correctly for all types of evolving faults.The innovative and fast measuring algorithm detects and blocksincorrect operation during open CT circuits. In summary, RED521 is the most reliable solution for protecting the most essentialobjects of your power system.
RED 521 offers a compact solution that can be easily adaptedto different busbar configurations. Up to 18 current transformerscan be connected directly to the terminal. It is simple to engineerfor any application since only two operational settings and nointerposing auxiliary CTs are needed. The CT ratios are enteredas primary values from the front mounted HMI. This significantlyreduces both commissioning and installation time. RED 521 isthe ideal solution for your retrofits and new installations sinceit can be connected to the same CT cores as protection relayswithout auxiliary CTs.
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