Project Description

SEL-387/SEL-387A Current Differential and Overcurrent Relay

SEL-387 Current Differential and Overcurrent Relay

The SEL-387 Current Differential and Overcurrent Relay provides protection, control, and metering for transformers, machines, buses, breakers, and feeders. Features include four three-phase current inputs with independent restrained and unrestrained differential protection, programmable single- or dual slope differential characteristic, circuit breaker monitor, battery voltage monitor, and enhanced SELOGIC® Control Equations.

Functional Overview

49 Thermal Monitoring
50 (P,G,Q) Overcurrent (Phase, Ground, Neg. Seq.)
51 (P,G,Q) Time-Overcurrent (Phase, Ground, Neg. Seq.)
87 Three-Phase Current Differential
87G Restricted Earth Fault (REF)
DFR Event Reports
ENV SEL-2600
LGC SELogic Control Equations
SER Sequential Events Recorder
BRM Breaker Wear Monitor
SBM Station Battery Monitor

* Optional


Front- and Rear-Panel Diagrams

SEL-387 Front Panel SEL-387 Rear Panel
Front Rear



Protect power transformers with as many as four windings using a combination of single- or dual-slope percentage differential characteristics, overcurrent protection, and Restricted Earth Fault (REF) protection.


Reduce total project costs through remote communications capa-bilities and elimination of external control switches and indicating lamps. Use remote communications capabilities for control, moni-toring, and alarm purposes.


Locally control relay operation, and initiate or block automation sequences from remote sites or control systems.


Simplify fault and system disturbance analysis with event reports and sequential events recorder. Use breaker contact wear and substation battery voltage monitors to efficiently dispatch mainte-nance resources.

Specify optional thermal modeling per IEEE C57.91:1995 for mineral-oil immersed transformers. Use the thermal element to activate a control action or to issue an alarm when your transformer is in danger of excessive insulation aging or loss-of-life.



487E 387E 387 387A 787 787-3E 787-3S 787-4X 587
Breaker Failure Protection f f f f
Transformer and Machine Current Differential
Low-Impedance Bus Differential
Underfrequency Load Shedding f +
Undervoltage Load Shedding f +
Three-Phase Current Inputs 5 3 4 2 2 3 3 4 2
Three-Phase Voltage Inputs 2 1 1+ 1 1
24 Overexcitation (Volts/Hertz) +
25 Synchronism Check
27/59 Under-/Overvoltage +
32 Directional Power +
46 Current Unbalance
49 Equipment Thermal Monitoring +
50FO Flashover Protection f f f f f 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
67 (P,G,Q) Directional Overcurrent (Phase, Ground, Neg. Seq.)
81 Under-/Overfrequency +
81R Change-in-Rate-of-Frequency f
87 Current Differential
REF Restricted Earth Fault + +
SELogic Control Equations
Voltage Check on Closing f f f
Transformer Cooling Fan Control f f f f f
Nonvolatile Latch Control Switches
SELogic Remote Control Switches
SELogic Local Control Switches
Display Points
Multiple Settings Groups
Substation Battery Monitor
Breaker Wear Monitor
Event Report (Multicycle Data)
Sequential Events Recorder
Instantaneous Meter
Demand Meter
Load and Temperature Profile Report
RTD (Resistance Temperature Detector) Inputs + + + +
Built-In Web Server
IEEE C37.118 Synchrophasors
IEC 61850 + + + + + +
IEC 60870-5-103 + + +
Simple Network Time Protocol (SNTP)
Parallel Redundancy Protocol (PRP)
Through-Fault Monitor +
2600 RTD Module Communications
Thermal Model +
Connectorized (Quick Disconnect) Available + + + + + + +
Standard Feature
+ Model Option
f This function may be created using settings

Product Literature