Project Description

SEL-351/SEL-351A Protection System

SEL-351 Protection System
The SEL-351 Protection System has built-in Ethernet and IEEE C37.118 synchrophasors, and is ideal for directional overcurrent applications. Optional MIRRORED BITS® communications and power quality monitoring add flexibility to solutions. The SEL-351 is the protection standard for utility and industrial electrical systems around the world.

Functional Overview

16SEC Access Security (Serial, Ethernet)
25 Synchronism Check
27 Undervoltage
32 Directional Power*
50BF Breaker Failure Overcurrent
50G Best Choice Ground
50N Neutral Overcurrent
50 (P, G, Q) Overcurrent (Phase, Ground, Neg. Seq.)
50/51 Adaptive Overcurrent
51N Neutral Time-Overcurrent
51 (P, G, Q) Time-Overcurrent (Phase, Ground, Neg. Seq.)
52PB Trip/Close Pushbuttons*
59 Overvoltage
59 (P, G, Q) Overvoltage (Phase, Ground, Neg. Seq.)
67N Directional Neutral Overcurrent
67 (P, G, Q) Directional Overcurrent (Phase; Ground, SEF*; Neg. Seq.)
79 Autoreclosing
81 (O, U, R) Frequency (Over, Under, Rate)
85 SEL MIRRORED BITS Communications*
DFR Event Reports
HMI Operator Interface
LGC SELOGIC Control Equations
MET High-Accuracy Metering
PMU Synchrophasors
PQM Voltage Sag, Swell, and Interruption*
SER Sequential Events Recorder
BRM Breaker Wear Monitor
HBL Harmonic Blocking
LDE Load Encroachment
LDP Load Data Profiling*
LOC Fault Locator
PPV Phantom Phase Voltage
SBM Station Battery Mon

* Optional


Front- and Rear-Panel Diagrams

SEL-351 Front Panel SEL-351 Rear Panel
Front Rear


Complete Overcurrent Protection

Protect lines and equipment using phase, negative-sequence, residual-ground, and neutral-ground overcurrent elements with directional control.

Increased Overcurrent Element Security With Second-Harmonic Blocking

Use the second-harmonic blocking elements to detect transformer energization, and block selected tripping elements until inrush conditions subside.

Enhanced Breaker Monitoring

Inspect reports for the most recent trip and close operating times and average operating times, or gather trending data for up to 128 previous operations. This information allows timely and economical scheduling of breaker maintenance.

Fast Dropout Breaker Failure Element

Detect a failed circuit breaker with built-in breaker failure detection elements and logic.


451 351 351A 751 751A 551/
Distribution Feeder Protection
Breaker Failure Protection f f
Generator Intertie Protection + +
Synchronism Check + +
Underfrequency Load Shedding f
Undervoltage Load Shedding f +
27/59 Under-/Overvoltage +
32 Directional Power Elements f + +
49 Thermal Overload f
50 (P,N,G,Q) Overcurrent Element (Phase, Neutral, Ground, Neg. Seq.)
51 (P,N,G,Q) Time-Overcurrent Element (Phase, Neutral, Ground, Neg. Seq.)
67 (P,N,Q) Directional Overcurrent (Phase, Neutral, Neg. Seq.) +
81 Over-/Underfrequency
Separate Neutral Overcurrent
Load-Encroachment Supervision +
Mirrored Bits Communications +
Sensitive Earth Fault Protection + + +
Directional Sensitive Earth Fault Protection + +
Pilot Protection Logic
Rate-of-Change-of-Frequency (df/dt) f +
Harmonic Blocking +
Arc Sense Technology (AST) High-Impedance Fault Detection + +
Arc-Flash Detection + +
Phantom Phase Voltage
Current/Voltage Channels 6/6 4/4 4/4 4/4 4/4 4/0
Complete Two-Breaker Control
79 Automatic Reclosing + +
Fault Locating
SELogic Control Equations With Remote Control Switches
SELogic Counters
Voltage Check on Closing + +
Operator Control Pushbuttons
SELogic Nonvolatile Latch +
Nonvolatile Local Control Switches +
Display Points +
Multiple Settings Groups
Substation Battery Monitor + +
Breaker/Recloser Wear Monitor
Trip Coil Monitor f f f f f f
Voltage Sag, Swell, and Interruption (VSSI) +
Load/Signal Profile Recorder +
Sequential Events Recorder
Demand Meter +
DNP3 Level 2 Outstation + + +
Modbus Outstation +
IEEE C37.118 Synchrophasors
Bay Control
Ethernet + + +
IEC 61850 + + + + +
Simple Time Network Protocol (SNTP)
Independent Trip/Close Pushbuttons + + +
Harmonic Metering
RMS Metering
Standard Feature
+ Model Option
f This function may be created using settings

Product Literature