SEL Relay Families — Choosing the Right Relay
Key Takeaway
Major SEL relay product families — SEL-300, SEL-400, SEL-700 series, and application-specific relays — with selection criteria by voltage level, equipment type, and protection requirements.
Quick Answer
SEL organizes relays by application: SEL-300 series for transmission line protection, SEL-400 series for advanced transmission, SEL-700 series for generator and motor protection, SEL-351 for feeder overcurrent, SEL-387 for transformer differential, and SEL-651R for recloser control.
Major Families
- SEL-300 series — SEL-311 (distance), SEL-321 (distance + pilot), SEL-351 (overcurrent/feeder), SEL-387 (transformer differential)
- SEL-400 series — SEL-411L (line current differential), SEL-421 (advanced distance), SEL-451 (feeder distance+overcurrent)
- SEL-700 series — SEL-300G/400G (generator), SEL-710 (motor), SEL-749M (advanced motor)
- SEL-651R — Recloser control for distribution
- SEL-734 — Power quality and revenue metering
Selection Criteria
- Voltage level (distribution vs transmission)
- Equipment type (line, transformer, generator, motor, bus)
- Required protection functions
- Communication requirements
- Available CT and VT inputs
Frequently Asked Questions
The SEL-351 series is one of the most widely deployed feeder protection relays, providing phase and ground overcurrent, directional overcurrent, reclosing, and metering.
SEL-387 and SEL-487E provide transformer current differential protection. The SEL-487E adds restricted earth fault and through-fault monitoring.
SEL-311 provides basic distance protection. SEL-321 adds advanced directional ground fault protection, pilot scheme logic, and additional programmable logic.