Project Description

SEL-487B Bus Differential and Breaker Failure Relay

SEL-487B Bus Differential and Breaker Failure Relay
The SEL-487B provides optimized 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.

Functional Overview

50 Overcurrent
51 Time-Overcurrent
87 Current Differential
16SEC Access Security (Serial, Ethernet)
27/59 Over-/Undervoltage
50BF Breaker Failure Overcurrent
85 SEL Mirrored Bits Communications
DFR Event Reports
HMI Operator Interface
LGC Expanded SELogic Control Equations
MET High-Accuracy Metering
RTU Remote Terminal Unit
SER Sequential Events Recorder
SBM Station Battery Monitor


Front- and Rear-Panel Diagrams

SEL-487B Front Panel SEL-487B Rear Panel
Front Rear



Protect bus systems with up to 21 terminals (21 CTs per relay, 63 CTs with a three-relay scheme), 6 protection zones, and 3 independent check zones. (For information about covering larger bus systems, contact us.) To optimize protection security, each check zone will supervise a designated phase in the system, and a patented open CT detection algo-rithmblocks potential misoperations during open or shorted CT conditions. Differential and directional current elements provide increased security and fast fault detection. Reduce protection costs with built-in breaker failure protection.


Implement different ratio CTs and nondedicated CTs with the SEL-487B Bus Differential and Breaker Failure Relay. Eliminate complex wiring by using CT ratios that differ by up to a factor of 10:1. Take advantage of the same CTs for differential protection, metering, backup relaying, and other functions.

Automation and Control

Reduce project costs and simplify interconnect wiring by using multiple communications protocols and ports. 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 voltage levels, and three-phase voltage are continuously monitored and updated.

Enhanced Security

Indicate the relay configuration, who accesses it, and at what access level, with programmable alarm bits.


487B 587Z
Breaker Failure Protection f
Bus Differential
High-Impedance Bus Differential
Low-Impedance Bus Differential
Three-Phase Current Inputs 7/10
Three-Phase Voltage Inputs 1
27/59 Under-/Overvoltage
46 Current Unbalance f
50 (N,G) Overcurrent (Neutral, Ground)
50P Phase Overcurrent
50Q Negative-Sequence Overcurrent
51 (N,G) Time-Overcurrent (Neutral, Ground)
51P Phase Time-Overcurrent
51Q Negative-Sequence Time-Overcurrent
87 Current Differential
87Z High-Impedance Differential
Single-Pole Trip/Close
Three-Phase Differential Bus Zones 2/3/6 1
Check Zones 3
79 Automatic Reclosing f
Dynamic Zone Selection
SELogic Control Equations
Nonvolatile Latch Control Switches
SELogic Remote/Local Control Switches
Display Points
Multiple Settings Groups
Substation Battery Monitor
Event Report (Multicycle Data)
Sequential Events Recorder
Instantaneous Meter
Demand Meter
IEC 61850 +
Built-In Web Server
Simple Network Time Protocol (SNTP)
Mirrored Bits Communications
Parallel Redundancy Protocol (PRP)
Connectorized (Quick Disconnect) Available +
Standard Feature
+ Model Option
f This function may be created using settings

Product Literature