Protect Transmission Lines With High-Speed Distance and Directional Functions.

Implement subtransmission, or Backup Distance Protection At A Very Low Cost With The SEL-311A Relay.

Economical Step Distance Protection Using The SEL-311B Relay With Four-Shot Reclosing And Synchronism Check. 

Apply The SEL-311C Relay For Complete Three-Pole Distance Protection, Monitoring, And Control Of Transmission Lines.

Use the SEL-311L Line Current Differential Relay With Integral Four Zone Distance Backup For Easy-to-Apply High-Speed Line Protection.

Use SEL-387L Line Current Differential Relays For Economical, Easy-To-Apply Line Protection.

The SEL-321 Relay Delivers Outstanding EHV Protection, Performance, And Features—At A Price Practical For All Voltage Levels And With The Features You Need for System Integration.