html{display:none} SEL-487B Bus Differential and Breaker Failure Relay | Schweitzer Engineering Laboratories


Bus Differential and Breaker Failure Relay

The SEL-487B provides optimized, low-impedance bus differential fault detection by using high-speed, subcycle protection coupled with high-security operation for external faults. Superior protection performance is combined with integrated station automation features for seamless transition into new and retrofit applications. Optional Time-Domain Link (TiDL) technology and SEL Sampled Values (SV) technology using IEC 61850-9-2 transform the way you modernize your substation.

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Low-Impedance Bus Differential Protection—Provide flexible low-impedance bus differential protection for various busbar topologies and sizes. You can protect systems with up to 21 three-phase bus terminals by using three relays to provide 6 three-phase differential bus zones and 3 independent check zones. Patented open CT detection algorithms block potential misoperations due to open or shorted CT conditions.

Integrated Overcurrent Protection—Choose from ten overcurrent curves for each current input for additional protection. Each torque-controlled time-overcurrent element has two reset characteristics. There is also one level of instantaneous and definite-time elements available for each current input.

Voltage Elements—Supervise current differential tripping within the relay by using voltage elements. Three separate voltage elements consist of two levels of phase under- and overvoltage elements and two levels of negative- and zero-sequence overvoltage elements for each of the three analog voltage quantities measured.

10:1 CT Ratio Mismatch—Install the SEL-487B in a system with nondedicated CTs, with CT ratio mismatches up to 10:1. This allows the same CTs to be used in other protection applications, such as metering or backup relaying.

Dynamic Zone Configuration—Automatically reassign current inputs to different bus zones without using auxiliary relays. The SEL-487B is suited for bus topologies that include bus-tie breakers and disconnects.

Breaker Failure Detection—Mitigate circuit breaker failure with the SEL-487B relay’s integrated circuit breaker failure detection and logic, which includes retrip capability for each terminal.

Integration and Automation—Select from an array of communications features and protocols to integrate the SEL-487B into your existing communications schemes. The relay features EIA-232 as well as optional copper or fiber Ethernet ports to fit into an array of applications. Protocol options include Mirrored Bits communications, DNP3 LAN/WAN, the Simple Network Time Protocol (SNTP), the Parallel Redundancy Protocol (PRP), the IEEE 1588 Precision Time Protocol Version 2 (PTPv2), and IEC 61850 Edition 2.

Digital Secondary System Technologies—TiDL and SEL SV technologies replace copper with fiber to increase safety, reduce costs associated with using copper, improve reliability, and limit the impact of an electromagnetic pulse. Apply the SEL-487B-2 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-487B-2 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.

Distributed Bus Protection—Apply the SEL-487B in a distributed bus protection scheme using TiDL technology. The system is easily scalable for the number of bays in your system, and it does not require special communications ports or network engineering.


    1. 1

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

    2. 2

      LCD automatically scrolls between custom displays.

    3. 3

      Easy-to-use keypad aids simple navigation.

    4. 4

      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 customization.

    1. 1

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

    2. 2

      Communications protocols include FTP, Telnet, 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.

    3. 3

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

    4. 4

      21 current and 3 voltage channels accommodate different busbar configurations.

    5. 5

      Choose from power supply options such as 24–48 Vdc; 48–125 Vdc or 110–120 Vac; or 125–250 Vdc or 110–240 Vac.

    1. 1

      4U chassis with horizontal mounting options (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 over the network.

    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.



Provide flexible, subcycle, low-impedance bus differential protection for various busbar topologies and sizes with the SEL-487B. You can protect systems that have up to 21 three-phase bus terminals by using three relays to provide 6 three-phase differential bus zones and 3 independent check zones. To optimize protection security, the check zones supervise the system on a per-phase basis and a patented open-CT detection algorithm blocks potential misoperations during open- or shorted-CT conditions. Directional and low-impedance differential current elements provide increased security and fast fault detection. Built-in breaker failure protection reduces protection costs.

Apply the same CT for differential protection, metering, backup relaying, or other functions. The SEL-487B relay can use nondedicated CTs with ratio mismatches up to 10:1.

Automation and Control
Reduce project costs and simplify interconnect wiring using multiple communications protocols. Configurable operator controls and simplified variable naming provide added power to SELogic control equations.

Monitoring and Metering
Provide accurate, timely monitoring and metering of busbar, feeder, and substation signals. Terminal currents, breaker and disconnect positions, station dc power levels, and three-phase voltage are continuously monitored and updated. You can eliminate external recorder and metering requirements with oscillographic and binary COMTRADE event reports and Sequential Events Recorder (SER) reporting.

acSELerator QuickSet SEL-5030 Software
Develop relay settings offline, program SELogic control equations, and analyze post-fault event reports.

Three Independent Check Zones
Improve power system availability and reliability by reducing unintentional relay operations due to failed or misaligned disconnect auxiliary contacts, and provide redundant verification of in-zone faults. Independent check zone settings offer additional flexibility for adjusting the check zone differential element.

Advanced Open CT Detection
Improve the security of the current differential element with patented open CT detection logic. It assures current differential bus zones will not misoperate due to terminals that can’t be properly measured.

Enhanced Front-Panel HMI
Improve efficiency and simplify installation with more target LEDs and operator pushbuttons. The 7U and 9U chassis have options for an additional 8 target LEDs and 4 operator pushbuttons, providing 24 target LEDs and 12 operator pushbuttons on the front-panel HMI.

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-487B-2 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-487B-2 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-487B-2 SV relay offers the traditional protection available in the SEL-487B-1 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-487B-2 SV relay can be used with other manufacturers’ SV-compliant units.

Simplified Settings Management
The SEL-487B-2 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-487B-2 relay with TiDL technology 
    • SEL-487B-2 relay (subscriber) with IEC 61850-9-2 Sampled Values
  • 1 A or 5 A CT inputs.
  • 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).
  • Add up to four expansion I/O cards with options for standard or high-speed contact outputs.
  • Rack- or panel-mount hardware packages.
  • Relay configurations:
    • One relay for up to 7 terminals and 2 three-phase zones.
    • Two relays for up to 10 terminals and 3 three-phase zones.
    • Three relays for up to 21 terminals and 6 three-phase zones.
    • Contact your local SEL sales representative for techniques on covering even larger systems.
  • Enhanced HMI with 24 target LEDs, 12 operator pushbuttons, and tricolor LEDs.
  • Connectorized hardware configuration.
  • 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-487B R124 SEL-487B-R124-V0-Z008004-D20131111 11/19/13 1133230001
SEL-487B-1 R317-V0 SEL-487B-1-R317-V0-Z017007-D20220523 6/10/22 ~1221610001
SEL-487B-2 R402-V0 SEL-487B-2-R402-V0-Z102101-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

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