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Protection System

The SEL-351 Protection System has built-in Ethernet and IEEE C37.118 synchrophasors, and is ideal for directional overcurrent applications. Optional Mirrored Bits communications and power quality monitoring add flexibility to solutions. The SEL-351 is the protection standard for utility and industrial electrical systems around the world.

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Breaker Failure Detection—Detect a failed circuit breaker quickly with built-in fast-reset breaker failure detection elements and logic.

Pilot Protection Schemes—Apply pilot protection on transmission, subtransmission, or distribution circuits, including three-terminal lines with traditional pilot communications equipment or with optional Mirrored Bits communications.

Grounded Power System Protection—Apply sensitive directional overcurrent protection for Petersen Coil grounded, ungrounded, and impedance-grounded power systems.

Service Restoration—Dispatch line crews to quickly isolate overhead line problems and restore service faster using the built-in fault locator.

Enhanced Circuit Breaker Monitoring—Schedule circuit breaker maintenance based on need as determined from detailed breaker monitoring data and alarms.

  • Integrate and automate substation equipment, even devices from multiple vendors, with the IEC 61850 communications protocol.
  • Protect and control radial or looped transmission, subtransmission, or distribution circuits.
  • Use pilot protection on transmission or subtransmission circuits, including three-terminal lines.
  • Apply directional and nondirectional overcurrent protection for a transformer/bus-main/bus-tie breaker.
  • Protect and control capacitor banks.
  • Apply breaker failure protection.
  • Control autoreclosing with synchronism and voltage check logic.
  • Protect small generators.
  • Protect distributed generation interconnections.
  • Shed load using underfrequency elements.
  • Add fault indicators to distribution protection, and reduce fault-finding time by 50 percent.
  • Dispatch line crews to quickly isolate overhead line problems and restore service faster using the built-in fault locator.
  • Schedule circuit breaker maintenance based on need as determined from breaker-monitoring data and alarms.
  • Analyze overcurrent protection system performance using the built-in Sequential Events Recorder (SER).
  • Use acSELerator QuickSet SEL-5030 Software to manage your relay settings.
  • Use acSELerator Team SEL-5045 Software to automatically gather relay event reports on your PC and manage them with a database.
  • Use synchroWAVe Event Software to display oscillograms and vector diagrams to analyze event reports.


  • IEC 61850 communications protocol
  • Front-panel USB communications port
  • SafeLock independent trip/close pushbuttons
  • Dual copper or single or dual fiber-optic Ethernet ports
  • Rack, panel, and projection mounting
  • 2U and 3U enclosure heights
  • Horizontal and vertical orientations
  • Mirrored Bits communications and load profiling
  • Additional I/O board with contact-sensing inputs and standard or high-current interrupting contact outputs
  • Sensitive directional power elements
  • Voltage sag, swell, and interruption recording
  • Low-range neutral current input channel for nondirectional sensitive earth fault (SEF) applications
  • Low-range neutral current channel for directional control for Petersen coil-grounded, high-impedance-grounded, or ungrounded power systems
  • Conformal coating—Protects equipment from harsh environments and airborne contaminants, such as hydrogen sulfide, chlorine, salt, and moisture


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Minimum QuickSet Version

Minimum QuickSet Version

Product Certifications