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Overcurrent/Reclosing Relay

The SEL-551 Overcurrent/Reclosing Relay replaces the many relays, control switches, and wiring required in traditional distribution substation protection and control panels. The relay also replaces line recloser control packages at a fraction of the cost. 

SEL-551/SEL-551C and SEL-851 Comparison


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Asset Protection—Monitor and protect distribution feeders, distribution buses, transformers, capacitors, or circuit breakers.

Current Transformer (CT) Connection Versatility—Connect the separate neutral-current input to accommodate core-balance CTs, separate neutral CTs, tertiary-winding CTs, or CT ground-residual circuits.

Reclosing Control—Coordinate with downstream reclosers using sequence coordination logic to program up to four reclosing attempts.

Field-Proven Ruggedness—Program SELogic control equation inputs and outputs to meet application needs in multiple environments. A wide operating temperature range (–40° to +85°C) allows installation in a control house or outdoor enclosure.


Comprehensive Overcurrent Protection
The SEL-551 provides phase, negative-sequence, residual ground, and neutral overcurrent protection in a compact package, including a complete set of instantaneous, definite-time, and time-overcurrent elements.

acSELerator QuickSet SEL-5030 Software
QuickSet helps speed up the relay application by allowing you to develop relay settings offline, program SELogic control equations, and analyze post-fault event reports.

Protection and Control Logic
SELogic control equations with SELogic variables and timers allow traditional or advanced protection schemes. Programmable local control elements permit front-panel pushbutton control. Programmable text display points provide enhanced local operator information.

Monitoring and Reporting
The SEL-551 features Instantaneous, peak, and demand metering. The latest twenty 15-cycle oscillographic data event reports and the latest 512 Sequential Events Recorder (SER) records are stored in nonvolatile memory.

The front-panel EIA-232 serial port, the rear-panel EIA-232/EIA-485 serial port, and the ASCII, binary, and Modbus RTU protocols enhance integration capabilities.

  • Panel-mount or rack-mount hardware package.
  • Connectorized packaging includes high-current interrupting output contacts.
  • Rear EIA-232 or EIA-485 serial communications port—either port includes a demodulated IRIG-B time-code input.
  • Bracket with mounting hole for FT-1 switch (switch not included) to mount one SEL-500 series relay in a 19-inch rack.
  • Conformal Coating: Protect equipment from harsh environments and airborne contaminants, such as hydrogen sulfide, chlorine, salt, and moisture.

Minimum Software Version

Latest Firmware Versions

There are no firmware versions available for this product.

Product Revision Firmware ID Date Available Serial Number
SEL-551 R600 SEL-551-R600-Vf-Z003002-D20210406 4/23/21 ~1211130001
Conventional Terminal Blocks
SEL-551 R514 SEL-551-R514-Vf-Z002002-D20110408 4/14/11 1111190001
Plug-In Connectors (Connectorized®)

Please contact Application Engineer for firmware related to your hardware platform.  The current revision does not apply to all hardware.

The Firmware IDs for older versions of the firmware can typically be found in Appendix A of the instruction manual.

Minimum Software Version

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501 551 551C 587Z - Software Tab


acSELerator QuickSet SEL-5030 Software

QuickSet is a tool for engineers and technicians to quickly and easily configure, commission, and manage power system devices. QuickSet includes a Graphical Logic Editor and a device template tool to reduce configuration time and streamline deployment.

Learn more and download on the SEL-5030 software page.

Visualization & Analysis

SEL-5601-2 synchroWAVe Event Software

synchroWAVe Event helps engineers diagnose a protective relay’s behavior during a power system fault. It is a powerful and easy-to-use solution for displaying and analyzing SEL relay event reports and COMTRADE files.

Learn more and download on the SEL-5601-2 software page.

Product Certifications