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 and platform: SEL-300/400 series for many transmission and feeder applications, SEL-700 series for distribution feeder, motor, and generator protection, plus application-specific models such as SEL-387/487E (transformer differential) and SEL-651R (recloser control).
Major Families
- SEL-300 series — SEL-311C/311L (transmission line), SEL-321 (distance + pilot), SEL-351 (feeder overcurrent), SEL-387 (transformer differential), SEL-300G (generator)
- SEL-400 series — SEL-411L (line current differential), SEL-421 (advanced distance), SEL-451 (protection + automation), SEL-400G (generator)
- SEL-700 series — SEL-751/751A (feeder), SEL-710 (motor), SEL-749M (advanced motor), SEL-700G (generator)—not the same as SEL-300G/400G
- 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
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Frequently Asked Questions
The SEL-351 series remains widely deployed for feeder overcurrent, directional overcurrent, reclosing, and metering. Newer distribution feeders often use SEL-751 family relays.
SEL-387 and SEL-487E provide transformer current differential protection. The SEL-487E adds restricted earth fault and through-fault monitoring.
SEL-311 provides distance protection for lines. SEL-321 adds advanced directional ground-fault protection, pilot scheme logic, and additional programmable logic.
Still have questions about your setup? Talk to an engineer or call (210) 405-4248.