Project Description

SEL-700G Generator Protection Relay

SEL-700G Generator Protection Relay
The SEL-700G Relay is the right solution for utility and industrial generator protection, with an autosynchronizer, flexible I/O, and advanced communications. Apply the SEL-700G Relay for comprehensive primary and backup generator protection.

The SEL-700G provides a complete protection and synchronization solution for synchronous generators. Eliminate the complexity and cost of standalone synchronizer packages. Integrating the synchronization capability into the generator protection relay provides the most cost-effective and reliable solution.

Easily upgrade protection without cutting or drilling existing cutouts with a small form factor and multiple mounting adapters. Quickly integrate into serial- or Ethernet-based communications with Modbus®, DNP3, IEC 61850,MIRRORED BITS® communications, DeviceNet™, and other protocols.

Functional Overview

SEL-700G Functional Overview
Compensator Distance, Voltage Restrained/Controlled Time-Overcurrent
24 Volts/Hertz
25G Synchronism Check
27 Undervoltage
32 Directional Power
40 Loss-of-Field
46 Neg. Seq. Overcurrent
49R Thermal Overload (RTD)
49T Thermal Model
50N Neutral Overcurrent
50 (P,G,Q) Overcurrent (Phase, Ground, Neg. Seq.)
51G Ground Time-Overcurrent
51N Neutral Time-Overcurrent
59N (64G1) Neutral Overvoltage
59S Synchronism Overvoltage
59 (P,G,Q) Overvoltage (Phase, Ground, Neg. Seq.)
60 Loss-of-Potential
64F Field Ground
64G 100 Percent Stator Ground
67G Directional Ground Overcurrent
67N Directional Neutral Overcurrent
78 Out-of-Step
81 (O,U,R) Frequency (Over, Under, Rate)
87 Three-Phase Current Differential
87N Neutral Current Differential
REF Restricted Earth Fault
52PB Pushbutton Trip/Close
85 SEL Mirrored Bits Communications
BF Breaker Failure
BRM Breaker Wear Monitor
DFR Event Reports
ENV SEL-2600
HMI Operator Interface
LDP Load Data Profiling
LGC SELogic Control Equations
MET High-Accuracy Metering
PMU Synchrophasors
SER Sequential Events Recorder
RTU Remote Terminal Unit


Front- and Rear-Panel Diagrams

SEL-700G Front Panel SEL-700G Rear Panel
Front Rear


Comprehensive Generator Protection

Connect the SEL-700G Generator Protection Relay across small, medium, or large generators forcomplete primary and backup protection. Adding the neutral voltage connection provides 100 percent stator ground protection, based on fundamental-frequency and third-harmonic neutral-voltage measurements. Connecting the neutral current input provides protection for solidly grounded or resistance-grounded machines.


Replace external generator control and synchronizer relays with the built-in automatic synchronizer function. Frequency, voltage, and phase control of the generator are automatically synchro-nized and connected to the power system. Monitor the generator synchro-nization process using generator start reports and the PC-based synchroscope.

Current Differential Protection

Apply sensitive percentage-restrained current differential elements and an unrestrained element, along with synchronism check and volts-per-hertz elements, across the entire unit to protect both the generator and the step-up transformer. Optional current differential elements detect stator faults using a secure, sensitive current differ-ential function. Power transformer and CT connection compensation allows the unit step-up transformer to be included in the generator differential zone.

Breaker Wear Monitoring

Record accumulated breaker contact wear with the breaker monitor function, which uses the manufacturer’s speci-fications for defining breaker operation limits. The internal monitor tracks the total number of close/open operations and integrates the interrupted current per phase. Set an alarm to alert opera-tors when measured and accumulated quantities approach maintenance thresholds. This information facilitates proactive breaker maintenance and replacement without underutilizing resources.

Easy Communications

Choose from single or dual copper or fiber-optic Ethernet ports, or serial communications, and several protocols, including Mirrored Bits®communications and IEC 61850. Pick multiple Modbus® TCP or Modbus serial sessions for custom configuration of your application. Use DNP3 Serial or DNP3 LAN/WAN protocols.



300G 700G 547
Generator Protection
Induction Motor Protection
Breaker Failure Protection f f
Equipment Thermal Monitoring + +
Generator Intertie Protection
Synchronism Check + +
Integrated Synchronizer +
21P Phase Mho or Compensator Distance +
24 Overexcitation (Volts/Hertz)
27/59 Under-/Overvoltage
32/37 Directional/Underpower Elements
40 Loss-of-Field
46 Current Unbalance
47 Phase Reversal
49 Thermal
50 (P,N,G) Overcurrent (Phase, Neutral, Ground)
50Q Negative-Sequence Overcurrent
51 (N,G) Time-Overcurrent (Neutral, Ground)
55 Power Factor f f
60 Loss-of-Potential
64G 100 Percent Stator Ground +
64F Field Ground
67 (N,G) Directional Overcurrent (Neutral, Ground)
78 Out-of-Step
81 Over-/Underfrequency
87 Current Differential + +
87G Restricted Earth Fault
Separate Neutral Overcurrent
Inadvertent Energization f f
Flashover Protection f f
SELogic Control Equations/Remote Control Switches
Nonvolatile Latch Control Switches
Multiple Settings Groups
Station Battery Monitor
Breaker Wear Monitor
Event Report (Multicycle Data)/Sequential Events Recorder
Demand Meter
Load Profile Report
RTD (Resistance Temperature Detector) Inputs + +
Ethernet +
IEC 61850 +
Simple Network Time Protocol (SNTP)
Modbus TCP
Modbus RTU Outstation +
Synchrophasors With IEEE C37.118 Protocol
Mirrored Bits Communications
DeviceNet +
Accepts Wye or Open-Delta Voltage Transformers +
Connectorized (Quick Disconnect) Available +
Standard Feature
+ Model Option
f This function may be created using settings

Product Literature