Project Description

SEL-387E Current Differential and Voltage Relay

SEL-387E Current Differential and Voltage Relay

The SEL-387E Current Differential and Voltage Relay provides protection to two- or three-winding power transformers. Voltage inputs for power metering, overexcitation protection, and over-/underfrequency load shedding provide versatile solutions for power apparatus protection. Automation features reduce total project construction and operation costs through elimination of traditional external control switches, meters, and indicating lamps.

Functional Overview

24 Volts/Hertz
27 Undervoltage
50 (P,G,Q) Overcurrent (Phase, Ground, Neg. Seq.)
51 (P,G,Q) Time-Overcurrent (Phase, Ground, Neg. Seq.)
59 Overvoltage
81 (O,U) Over-/Underfrequency
87 Three-Phase Current Differential
87G Restricted Earth Fault
DFR Event Reports
HMI Operator Interface
LGC SELogic Control Equations
MET High-Accuracy Metering
SER Sequential Events Recorder
BRM Breaker Wear Monitor
SBM Station Battery Monitor
TRM Transformer Monitor

* Optional


Front- and Rear-Panel Diagrams

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



Expand transformer protection capabilities with restricted earth fault (REF), negative-sequence overcurrent, overexcitation, and frequency elements. Innovative restraint and blocking prevent false trips and enhance security while maintaining sensitivity to internal faults.


Simplify engineering designs with SELogic® control equations for customizing advanced protection and control schemes. Apply frequency elements for load shedding and/or load restoration schemes.


Oscillographic event reports, Sequential Events Recorder (SER) reporting, and accurate three-phase power metering reduce or eliminate external recorder and metering requirements. Station battery voltage monitor, through-fault monitor, and circuit breaker contact wear monitor assist maintenance programs.

Flexible Communications

Serial and Ethernet communications provide complete integra-tion. IEC 61850 communications offer high-speed, relay-to-relay information exchange. Supported protocols include ASCII, binary, and SEL distributed port switch communications. Built-in web server provides read-only point of access to view metering, settings, targets, and SER



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