Project Description

SEL-311L Line Current Differential Protection and Automation System

SEL-311L Line Current Differential Protection

Use the SEL-311L Line Current Differential Relay with integral four zone distance backup for easy-to-apply, high-speed line protection.

Apply subcycle current differential protection with included four zone distance and directional overcurrent backup. Use single or dual differential channels for reliability. Apply the SEL-311L on two- or three-terminal lines. Unique measuring elements provide coordination with tapped loads. Reduce total project construction and operation costs through integration of the included four-shot recloser and relay logic operators into your automation system.

Improve protection system reliability with continuous checks of communications quality, breaker wear, battery voltage, and relay health. Use the included LCD display in place of traditional panel meters.

Functional Overview

SEL-311L Function Overview

21 Phase and Ground Distance
25 Synchronism Check
50 Overcurrent
51 Time-Overcurrent
67 Directional Overcurrent
79 Autoreclosing
81 (O, U) Over-/Underfrequency
87L Current Differential
DFR Event Reports
LGC Expanded SELOGIC Control Equations
HMI Operator Interface
PMU Synchrophasors
SER Sequential Events Recorder
BRM Breaker Wear Monitor
LOC Fault Locator
SBM Station Battery Monitor


Front- and Rear-Panel Diagrams

SEL311L- Front Panel SEL311L- Rear Panel
Front Rear



Apply single-pole or three-pole subcycle current differential protection. Reduce protection system costs by using built-in distance and/or overcurrent backup functions.


Innovative operating characteristic makes settings easy. No fault studies are required for most differential applications.


Use single or dual channels for reliability. Apply on two- or three-terminal lines with or without tapped lines.


Incorporate synchrophasor measurements into wide-area protection and control systems. Use high-accuracy time correlation to improve event report analysis.


Reduce total project construction and operation costs by integrating four-shot recloser and relay logic operators into your automation system.


Improve station integration with serial and Ethernet communications. Use IEC 61850 communications for interoperability between relays with a select-before-operate function for added operational security. Increase communications dependability with dual failover Ethernet.



411L 421 311C 311L 387L
Distance Protection
Line Current Differential
Breaker Failure Protection f f
Undervoltage Load Shedding f f f f
Series-Compensated Lines + +
21G Mho Ground Distance
21XG Quad Ground Distance
21P Mho Phase Distance
25 Synchronism Check
27/59 Under-/Overvoltage f
49 Thermal 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 (N,G) Directional Overcurrent (Neutral, Ground)
67P Phase Directional Overcurrent
67Q Negative-Sequence Directional Overcurrent
81 Under-/Overfrequency
87L Line Current Differential
Programmable Analog Math
Out-of-Step Block and Trip
Load-Encroachment Supervision
Single-Pole Trip + +
Zone/Level Timers
Pilot Protection Logic
79 Automatic Reclosing
Number of Controlled Breakers 2 2 1 1 1
Fault Locating
Traveling Wave Fault Location +
Subcycle Distance Elements + + +
SELogic Control Equations
Nonvolatile Latch Control Switches
SELogic Remote Control Switches
SELogic Local Control Switches +
Display Points +
Mirrored Bits Communications
Substation Battery Monitor
Breaker Wear Monitor
Trip Coil Monitor f f f f
Event Report (Multicycle Data)
Sequential Events Recorder
Instantaneous Meter
DNP3 Level 2 Outstation + +
IEC 61850 Communications + + + +
Synchrophasors (SEL Format)
Synchrophasors (IEEE C37.118 Format)
Accepts Delta Voltage Transformers +
Connectorized (Quick Disconnect) Available + + +
Configurable Labels +
Standard Feature
+ Model Option
f This function may be created using settings

Product Literature