html{display:none} SEL-451 Protection, Automation, and Bay Control System | Schweitzer Engineering Laboratories


Protection, Automation, and Bay Control System

The SEL-451 is a complete standalone system. It has the speed, power, and flexibility to combine complete substation bay control with high-speed breaker protection in one economical system. You can use the SEL-451 as an integral part of a full substation protection, control, and monitoring solution. It reduces maintenance costs by accurately tracking the breaker operation. By monitoring breaker interruption times and the accumulated breaker duty, the SEL-451 helps you easily determine the need for proactive maintenance. You can integrate information with SCADA or automation systems through a communications processor or directly to the Ethernet port. Optional Time-Domain Link (TiDL) technology and SEL Sampled Values (SV) technology using IEC 61850-9-2 transform the way you modernize your substation.

SEL-400 Series Relay Mimic Diagrams

Starting At


Request a Follow-Up



Request a Follow-Up

Dual Breaker Bay Control—Meet your bay control needs with complete two-breaker control and high-speed breaker failure detection. You can easily control motor-operated switches, capacitor banks, and field I/O from the relay front panel or remotely. Configurable labels enable customization of relay controls to match your application.

Rapid Bay Control Commissioning—Choose among different bus configurations, including single- and dual-busbar, transfer bus, tie-breaker, breaker-and-a-half, ring-bus, double-bus/ double-breaker, and source-transfer configurations. These bus arrangements allow easy status and control of as many as 20 disconnect switches and two breakers.

High-Impedance Fault Detection—Detect high-impedance faults with Arc Sense technology (AST). High-impedance faults are a common result of a downed conductor on surfaces with poor conductivity. With AST, the SEL-451 alarms or trips for faults that produce low fault current and are undetectable with conventional overcurrent relays.

Complete Overcurrent Protection—Customize distribution protection with multiple instantaneous and time-overcurrent elements combined with SELogic control equations. Best Choice Ground Directional Element logic optimizes directional element performance and eliminates the need for many directional settings.

Pad-Mounted Switchgear Protection—Protect pad-mounted switchgear with low-energy analog (LEA) voltage inputs; this helps you save in overall system cost by eliminating the need for amplification electronics between the line sensor and the relay. Having fewer devices also leads to a simpler system, a reduction in labor costs, and the elimination of a possible point of failure.

Breaker Wear Monitoring—Compare published data from the breaker’s manufacturer to the actual interrupted current and number of operations for two breakers, and create alarms accordingly. You can monitor mechanical and electrical interruption time per pole, comparing average and last trip times for maintenance scheduling.

Digital Secondary System Technologies—TiDL and SEL SV technologies replace copper with fiber to increase safety, reduce costs, improve reliability, and limit the impact of an electromagnetic pulse. Apply the SEL-451-6 TiDL relay with the SEL-TMU TiDL Merging Unit in the field to provide remote I/O and communicate digitized analog signals over fiber optics. This simple point-to-point solution with a strong cybersecurity posture is easy to implement, with no external time source or network engineering required. Apply the SEL-451-6 SV relay to receive IEC 61850-9-2 SV data from a remote merging unit via a network. TiDL and SV relays are configured using SEL Grid Configurator software, which simplifies settings management.


    1. 1

      EIA-232 front serial port is quick and convenient for system setup and local access.

    2. 2

      Interactive bay display with user-configurable apparatus labels allows the operator to view the status of breakers and disconnect switches and to control them.

    3. 3

      Easy-to-use keypad aids simple navigation.

    4. 4

      Front-panel LEDs indicate custom alarms and provide fast and simple information to assist dispatchers and line crews with rapid power restoration.

    5. 5

      Programmable operator pushbuttons with user-configurable labels allow front-panel customization.

    1. 1

      Choose from a vertical or horizontal, panel-mount or rack-mount chassis and different size options.

    2. 2

      Use a maximum of 68 output contacts. Requires 8U chassis.

    3. 3

      Communications protocols include FTP, Telnet, synchrophasors, DNP3 LAN/WAN, the Parallel Redundancy Protocol (PRP), IEC 61850 Edition 2 (optional feature), and the IEEE 1588 Precision Time Protocol Version 2 (PTPv2). For PTPv2 implementation, Ports 5A and 5B must be ordered as an option.

    4. 4

      Use three rear EIA-232 ports for Mirrored Bits communications, DNP3, SCADA, and engineering access.

    5. 5

      Use a maximum of 103 input contacts. Requires 8U chassis.

    6. 6

      Order six current inputs in standard terminal blocks (as shown) or a Connectorized hardware configuration.

    7. 7

      Choose six voltage inputs in either standard terminal blocks, a Connectorized hardware configuration, or a low-energy analog (LEA) hardware configuration.

    8. 8

      Power supply options include: 24–48 Vdc; 48–125 Vdc or 110–120 Vac; or 125–250 Vdc or 110–240 Vac.

    1. 1

      4U chassis with mounting options (vertical or horizontal; panel or rack) accommodates your application needs.

    2. 2

      LEDs indicate the connection status to an SEL-TMU TiDL Merging Unit on a per-port basis.

    3. 3

      Eight 100 Mbps fiber-optic ports allow the TiDL relay to connect with eight remote SEL-TMU devices and to receive remote analog and digital data.

    1. 1

      The 4U chassis has various mounting options to accommodate hardware needs.

    2. 2

      Select fiber-optic, copper, or mixed Ethernet with separate ports for SV data and engineering access.



Transformer Inrush Harmonic Monitoring
Apply the second-, fourth-, and fifth-harmonic elements with individual threshold settings to detect transformer energization and overexcitation conditions. The output from these harmonic detection elements can be used for a variety of functions, including modification of relay settings to improve security and event reporting to make identification of transformer energization events fast and simple.

Built-In Web Server
Access basic relay information on a standard Ethernet network with the built-in web server. You can view relay status, Sequential Events Recorder (SER) information, metering information, and settings with easy access within a local network. The web server access requires a relay password and is limited to read-only viewing of information.

Simple Network Time Protocol (SNTP)
Simplify wiring and installation by receiving a time signal over existing Ethernet networks. SNTP makes a good backup to more accurate IRIG-B time synchronization. The 5 ms accuracy is good for basic time synchronization throughout a substation.

Maximize the Capability of Substation Equipment
Fully load equipment by monitoring power, including thermal or rolling interval demand as well as peak demand on positive-, negative-, and zero-sequence current. Use the full capacity of the equipment while maintaining SEL quality protection.

Advanced Visualization Tools
The SEL-451 offers a configurable HMI for easy integration into your application or operating standards. HMI tools include custom metering and status displays, direct pushbutton access, critical information alarms in chronological order, a rotating display, and time-stamped SER reports. You can reduce errors by automatically scrolling between one-line bay diagrams, custom metering displays, and alarms.

Bay Control for Two Breakers
Complete two-breaker control and breaker failure complement the versatility of the SEL-451 programmable logic to meet your bay control needs. Easily control motor-operated switches, capacitor banks, and field I/O from the front panel or remotely. Configurable labels make it easy to customize relay controls to match your application.

Flexible Communications

  • An Ethernet card option provides two copper or fiber ports for failover redundancy.
  • Simplify Ethernet network topology and reduce external equipment with dual Ethernet ports that offer a switched mode for looped Ethernet networks.
  • Available Ethernet communications protocols include FTP, Telnet DNP3, LAN/WAN, the IEEE 1588 Precision Time Protocol Version 2 (PTPv2), IEC 61850 Edition 2, IEEE C37.118 synchrophasors, and the Parallel Redundancy Protocol (PRP).
  • All four independent EIA-232 serial ports support enhanced SEL Mirrored Bits communications, SEL Fast Message, SEL ASCII, Compressed ASCII, SEL Fast Operate, SEL Fast Meter, SEL Fast SER, and DNP3 Level 2 Slave.

Improve Operation With IEEE Synchrophasor Data
Give operators critical system information via serial or Ethernet communications. With the SEL-451, you get the required substation protection, monitoring, and control in addition to a built-in phasor measurement unit at each substation. The relay makes control decisions based on voltage, current, or frequency data from other relays. The synchrophasor real-time control (RTC) capability makes this information available for local or system-wide control and automation.

High-Accuracy Timestamping
Time-tag binary COMTRADE event reports with real-time accuracy of better than 10 µs. You can view system state information at the time of faults, or with timed triggers, across the entire system. This system state information helps validate system models and improve transfer limits and system stability.

Digital Fault Recording (DFR)
Combine relaying reliability with true DFR functionality. The SEL-451 Relay’s high-speed sampling (8 kHz) and COMTRADE output provide advanced oscillography. The acSELerator QuickSet SEL-5030 Software graphical user interface makes it easy to view harmonic analysis and events.

Integrate Many Substation Devices Into One Powerful System Using the SEL-451
Control cooling fans, motor-operated switches, or other equipment using the processing and I/O of the SEL-451. Hardware options let you expand I/O up to 103 inputs or 68 outputs.

Expanded SELogic Control Equations
Use math and logic combinations of analog and digital values for customized applications, adapt system control based on prefault conditions, and scale analog values and latch momentary inputs for SCADA retrieval.

acSELerator QuickSet Software
Help speed up relay applications by developing relay settings offline, programming SELogic control equations, and analyzing post-fault event reports.

Voltage Sag, Swell, and Interruption (VSSI) Report
Capture power quality data related to voltage disturbances over a long period of time.

Time-Domain Link Technology
Apply a TiDL solution, where SEL-TMU devices are placed in the yard close to the primary equipment to digitize discrete I/O signals and analog data and then transport them over a fiber-optic cable to the SEL-451-6 TiDL relay in the control house. Each SEL-TMU can share data with as many as four TiDL relays, providing protection design flexibility and reducing device count. TiDL technology uses point-to-point connections and a non-Ethernet protocol, providing a simple and secure solution. Because it does not need an external time source or Ethernet switches, it is easy to implement with no network engineering required. TiDL combines the proven protection of the SEL-400 series relays with the purpose-built SEL-TMU, reducing training requirements, simplifying deployment, and increasing availability. TiDL also provides built-in time synchronization and synchronous sampling, ensuring protection is available in the relay regardless of whether an external time signal is available.

SEL Sampled Values Technology
Implement an SEL SV solution, where the merging unit (publisher) digitizes analog signals from primary equipment and then transmits them to an SEL-451-6 SV relay (subscriber) in the control house via a fiber-based Ethernet network. The system uses precise time synchronization via IRIG-B or PTP. The SEL-451-6 SV relay offers the traditional protection available in the SEL-451-5 and can also receive SV data from devices such as the SEL-401 Protection, Automation, and Control Merging Unit or the SEL-421-7 Protection, Automation, and Control System Merging Unit. Because all SEL SV devices are compliant with IEC 61850-9-2 and the UCA 61850-9-2LE guideline, the SEL-451-6 SV relay can be used with other manufacturers’ SV-compliant units.

Simplified Settings Management
The SEL-451-6 TiDL and SV relays are configured using SEL Grid Configurator, a new software tool that increases efficiency and improves settings insights. It features a spreadsheet-style editor, protection visualization, comprehensive reporting, custom filters, and multiple-device settings management.

  • Digital secondary system solutions.
    • SEL-451-6 relay with TiDL technology.
    • SEL-451-6 relay (subscriber) with IEC 61850-9-2 Sampled Values.
  • Rack- or panel-mount horizontal or vertical hardware packages.
  • Ethernet connection options for primary and standby connections:
    • 10/100BASE-T
    • 100BASE-FX
  • IEC 61850 Edition 2 communications and IEEE 1588 Precision Time Protocol Version 2 (PTPv2).
  • One, two, or four additional I/O boards with standard, high-interrupting, or high-speed/high-interrupting outputs.
  • User-configurable labels for operator controls and target LEDs.
  • Connectorized hardware configuration.
  • Enhanced HMI with 24 target LEDs and 12 operator pushbuttons.
  • Independent breaker trip/close pushbuttons with status indication, including 24 additional input and 4 additional output contacts.
  • High-impedance fault detection using AST.
  • 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-451-1 R202 SEL-451-1-R202-V0-Z004004-D20090213 2/27/09 2009058001
SEL-451-2 R126 SEL-451-2-R126-V0-Z100011-D20121207 12/21/12 1123560001
SEL-451-4 R126 SEL-451-4-R126-V0-Z100011-D20121207 12/21/12 1123560001
SEL-451-5 R327-V0 SEL-451-5-R327-V0-Z030014-D20221209 12/9/22 1223430001
SEL-451-6 R403-V0 SEL-451-6-R403-V0-Z103102-D20220517 6/8/22 ~1221590001

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

Minimum Software Version

Sales Resource Central access is required to view the content in this tab.

Sales Resource Central

Product Certifications