Project Description

SEL-487E Transformer Protection Relay

SEL-487E Transformer Protection Relay

Protect and monitor most transformer applications with the powerful SEL-487E Transformer Protection Relay. Apply up to 5 three-phase restraint inputs, three independent restricted earth fault protection elements, and 2 three-phase voltage inputs, all with synchrophasors. Limit transformer damage by responding to internal fault conditions in less than 1.5 cycles.

Avoid catastrophic transformer failure by detecting turn-to-turn faults involving as little as 2 percent of the total winding. Minimize commissioning time and eliminate costly errors with software that recommends matrix compensation settings. Through-fault and thermal monitoring allows you to track transformer wear and schedule maintenance as necessary. Breaker wear monitoring reduces inefficient and costly breaker maintenance, saving time and money.

Functional Overview

16SEC Access Security (Serial, Ethernet)
24 Volts/Hertz
25 Synchronism Check
27 Undervoltage
32 Directional Power
46 Current Unbalance
49 Thermal
50BF Breaker Failure Overcurrent
50N Neutral Overcurrent
50 (P,G,Q) Overcurrent (Phase, Ground, Neg. Seq.)
51N Neutral Time-Overcurrent
51 (P,G,Q) Time-Overcurrent (Phase, Ground, Neg. Seq.)
59 Overvoltage
67 (P,G,Q) Directional Overcurrent (Phase, Ground, Neg. Seq.)
81 (O,U) Over-/Underfrequency
85 SEL Mirrored Bits Communications
87 (U,R,Q) Transformer Differential (Unrestrained, Restrained, Neg. Seq.)
DFR Event Reports
ENV SEL-2600
HMI Operator Interface
LGC Expanded SELogic Control Equations
MET High-Accuracy Metering
PMU Synchrophasors
REF Restricted Earth Fault
RTU Remote Terminal Unit
SER Sequential Events Recorder
BRM Breaker Wear Monitor
LDP Load Data Profiling
SBM Station Battery Monitor
TRM Transformer Monitor

* Optional


Front- and Rear-Panel Diagrams

SEL-487E Front Panel SEL-487E Rear Panel
Front Rear


Multiwinding Protection

Configure the SEL-487E Transformer Protection Relay for transformer differential protection in transformer applications using up to five restraint currents. This includes single transformers with tertiary windings. Use three independent restricted earth fault (REF) elements for protection of grounded-wye windings.

Advanced Asset Monitoring

Track transformer wear with through-fault and thermal monitoring. Reduce inefficient and costly breaker maintenance with advanced breaker monitoring. Monitor substation dc power systems for out-of-tolerance voltage levels or excessive voltage ripple.

Dependable Backup Protection

Provide backup protection with five phase, negative-sequence, and zero-sequence overcurrent elements and ten configurable time-overcurrent elements. Set up breaker failure protection with subsidence detection to rapidly detect breaker failure and minimize system coordination times.

High-Speed, Adaptive Differential Protection

Implement a two-stage slope that automatically adapts to internal or external fault conditions, even with CT saturation and heavily distorted waveforms, for fast, sensitive, dependable, and secure differential protection. The adaptive differential element responds to internal fault conditions in less than 1.5 cycles.

Diverse Transformer Applications

Protect large transformers and auto-transformers with breaker-and-a-half high- and low-side connections. Also, configure for a typical two-winding transformer application, and use the remaining three-phase current inputs for feeder backup protection.

Sensitive Turn-to-Turn Fault Detection

Avoid catastrophic transformer failure. Detect turn-to-turn faults involving as little as two percent of the total winding with the patented negative-sequence differential element.

Generator Step-Up Protection

Protect generator step-up (GSU) transformers, and apply the built-in temperature measurement (requires the SEL-2600 RTD Module) for monitoring generator and transformer winding temperatures simultaneously. Apply the volts/hertz element for overexcitation protection of loaded and unloaded generator operating conditions. Set the directional power elements to detect forward and reverse power flow conditions to monitor and protect the GSU transformer in prime power, standby, base load, and peak-shaving applications. Verify generator breaker synchronization with built-in synchronism check elements.

Station Phasor Measurement Unit (PMU)

Improve power system quality with SEL synchrophasors (IEEE C37.118) from all 24 analog channels (6 voltage and 18 current sources) in your relay. Use synchrophasors over serial or Ethernet communications to easily detect reactive loop flows, turn state estimation into state measurement, and provide early warning of potential system instability. Implement real-time control by receiving synchrophasor messages from two PMUs, and take action based on local and remote messages.



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