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 transforms the way you modernize your substation.

Starting At

$6,830 USD

Request a Follow-Up


Low-Impedance Bus Differential Protection—Provide flexible low-impedance bus differential protection for various busbar topologies and sizes. 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. Implement the SEL-487B in 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, Modbus, 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.

TiDL Technology—Modernize your substation by applying the TiDL-enabled SEL-487B with the SEL-2240 Axion TiDL nodes. In a TiDL system, the Axion node provides remote I/O and digitizes analog signals over fiber optics for the relay. This simple and secure digital secondary system solution is easy to implement, with no external time source or network engineering required. Replacing copper with fiber increases safety, reduces costs associated with using copper, improves reliability, and limits the impact of an electromagnetic pulse.



Overview—TiDL Technology Rear Panel



How to Commission a Distributed Bus System With TiDL™-Enabled SEL-487B and SEL-2240 Axion®

Watch Video New
How to Commission a Distributed Bus System With TiDL™-Enabled SEL-487B and SEL-2240 Axion®

Provide flexible, subcycle, low-impedance bus differential protection for various busbar topologies and sizes with the SEL-487B. 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. Reduce protection costs with built-in breaker failure protection.

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. 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 Axion TiDL nodes 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 in the control house. This innovative technology uses point-to-point connections and a nonroutable 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 modularity of the Axion, reducing training requirements and providing a scalable and flexible solution. It also provides built-in time synchronization and synchronous sampling, ensuring protection is available in the relay regardless of whether or not an external time signal is available.

  • 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.


Documents sorted by newest first.



Minimum QuickSet Version

Product Revision Z Number Minimum Software Version
SEL-487B-1 R313-V0 013
SEL-487B-1 R311-V1 012

Minimum QuickSet Version

Product Revision Z Number Minimum Software Version
SEL-487B-1 R313-V0 013
SEL-487B-1 R311-V1 012

Product Certifications

By continuing to browse or by clicking “Accept All Cookies,” you agree to the storing of first- and third-party cookies on your device to enhance site navigation and analyze site usage for an improved user experience. View our Cookie Policy