Generator Protection

Apply SEL generator protection products and avoid expensive equipment damage and failure while maintaining system performance and increasing availability. SEL quality-tested features provide complete primary and backup protection from all types of faults. SEL’s power interconnection, protection, communications, control, and metering equipment is ideally suited for utility-, industrial-, and commercial-scale power generation systems. SEL solutions protect and control base load, peaking, and stand-by generators of every size and fuel type. Our automatic generation control (AGC) and synchrophasor technology give system operators unprecedented diagnostic and control capabilities to maximize power output, stability, efficiency, and reliability.

SEL products and systems protect and control generators and plants that use hydroelectric, coal, gas, geothermal, wind, biofuel, solar, and other energy sources. Upgrade to a proven SEL protection system today, and be confident that your generation system will be working tomorrow.

Advantages of an SEL Generator Protection Solution

  • Design a complete generator protection system, including advanced stator, field, and generator step-up (GSU) relaying.
  • Scale your solution across your generation fleet, from reciprocating standby units to large combined cycle plants and from traditional generation to distributed generation.
  • Integrate remote I/O, annunciators, and transformer monitors to increase unit monitoring and display for operators.
  • Select from multiple protocols for integration into plant control and transmission SCADA systems.
  • Employ software-defined networking (SDN) to increase the security and reliability of the control network.
  • Depend on high-quality SEL products, which lead the industry with the highest mean time between failures and include a ten-year, no-hassle warranty.
  • Meet and exceed revenue accuracy standards and monitor power quality by integrating an advanced meter.
  • Add a bullet at the end of the list under "Advantages of an SEL Generator Protection Solution" that says:
  • SEL generator protection products have a mean time between failures (MTBF) of over 900 years* and are backed by a ten-year warranty.
*This MTBF metric was calculated in June 2023.

Complete SEL Generator Protection Solution


Generator Protection

Numerous current, voltage, frequency, distance, power, and out-of-step elements in SEL generator protection relays provide comprehensive protection for large, medium, and small generators.


Use the optional, built-in automatic synchronizer function in either the SEL-700G Generator Protection Relay or SEL-400G to automatically synchronize the frequency, voltage, and phase angle of the generator and connect to the power system. This eliminates the need for expensive external synchronizing equipment.

Unit Protection

Apply sensitive percentage-restrained current differential elements and an unrestrained element, along with synchronism-check and volts-per-hertz elements, to protect both the generator and the step-up transformer. Harmonic-blocking elements protect the unit transformer bushing and end windings while maintaining security for inrush and through-fault conditions.

Metering and Reporting

View generator automatic synchronizer, SER, and 180-cycle oscillographic event reports in COMTRADE and CEV formats to analyze generator startup, shutdown, or system faults. SEL relays measure electrical, thermal, and generator run-time quantities.

STATOR/Field Ground Protection

With SEL generator relays, adding the neutral voltage connection provides 100 percent stator ground protection for most machines, based on third-harmonic voltage measurements. Connecting the neutral current input provides protection for solidly grounded or resistance-grounded machines. State-of-the-art voltage injection allows you to monitor field ground resistance.

Software-Defined Networking

Traditional Ethernet switches generally behave similarly regardless of the environment (one size fits all). With SDN, LAN switching can be tuned or optimized for the specific requirements of the environment. Only SEL has implemented SDN with the goal of optimizing an operational technology (OT) network. SEL SDN allows you to purpose-engineer networks like you purpose-engineer the power system.

Dual Differential Zone Protection

The SEL-400G Advanced Generator Protection System has two independent, universal differential elements, which provide protection for two independent protection zones. This allows separate generator and step-up transformer protection in a single device.

Advanced Time Synchronization

The SEL-2488 Satellite-Synchronized Network Clock receives Global Navigation Satellite System (GNSS) time signals and distributes precise time via multiple output protocols, including IRIG-B; the Precision Time Protocol (PTP) to serve as a grandmaster clock, as defined by IEEE 1588; and the Network Time Protocol (NTP).

Resistance Temperature Detector (RTD)-Based Thermal Protection

Acquire thermal data for alarm, monitoring, and trip functions in SEL relays with an external SEL-2600 RTD Module, which provides 12 RTDs.

Questions? Contact Us!

If you have any questions about SEL products, services, solutions, or support, please contact us. Our service and support professionals are ready to provide the answers you need.

Unbeatable Support

SEL support teams are stationed in regional offices around the world and staffed with application engineers who are experts in our products and in power system applications.

Technical support for SEL-manufactured devices is always free. No matter how often you need to call or how long your SEL products have been in service, you’ll reach an SEL expert who can provide the service and support you need.

Our cybersecurity team is always ready with the information and resources needed to keep your OT networks and critical systems secure and working effectively. Cyber services support contracts can include incident response, audits, system hardening, and more, depending on your anticipated needs.

More about SEL warranty and support