SEL-351S Feeder Protection and Breaker Control Relay

The SEL-351S is a multifunctional digital feeder protection relay manufactured by Schweitzer Engineering Laboratories, designed for medium voltage distribution feeder protection, breaker control, metering and fault analysis in utility and industrial substation systems. This SEL-351S integrates directional overcurrent, ground fault protection, autoreclosing logic and synchrophasor measurement within one compact unit, replacing multiple traditional electromechanical relays and auxiliary control devices. The SEL-351S remains a widely used spare and retrofit IED for distribution substation cabinet upgrades and maintenance work.

The SEL-351S supports flexible protection setting via SELogic programmable control equations and acSELerator configuration software. It offers phase overcurrent, negative-sequence overcurrent and residual ground overcurrent elements with directional supervision, and its Best Choice Ground Directional Element simplifies ground fault coordination on complex distribution networks. The SEL-351S includes up to four-shot auto-reclosing functions with synchronism and voltage check logic, plus an impedance-based fault locator to help field crews quickly identify fault locations on overhead and cable feeders. Built-in sequential event recording, breaker wear monitoring and voltage sag/swell capture functions enable comprehensive post-fault review and condition tracking.

This SEL-351S is equipped with rich communication options including Ethernet, fiber, RS485 and RS232 ports, supporting DNP3, IEC 61850 and MIRRORED BITS communications for inter-relay logic and assisted tripping schemes. The front-panel display and operator pushbuttons of the SEL-351S allow local status viewing, setting checking and manual breaker control; optional SafeLock trip and close buttons provide independent hard control for safe substation operation. It supports both 1A and 5A CT secondary inputs, works for 50Hz and 60Hz power systems, and adopts standard panel or 19-inch rack mounting for substation protection cabinets.

The SEL-351S is commonly deployed for radial feeders, loop distribution circuits, industrial plant incoming lines and capacitor bank protection. Replacing a failed protection unit with the SEL-351S restores selective feeder protection and breaker control rapidly, reducing outage duration for distribution networks. As a mature Schweitzer protection relay, the SEL-351S delivers stable fault response and interoperability with other SEL automation devices for distribution automation and restoration schemes.