Schweitzer Engineering Laboratories 0551003X531X Overcurrent Relay

The Schweitzer Engineering Laboratories SEL-551 Overcurrent/Reclosing Relay, part number 0551003X531X, is a microprocessor-based protective relay designed to provide fast overcurrent protection and automatic reclosing for distribution feeders. It monitors current through CT inputs and executes protection logic to trip the connected breaker on fault conditions while offering reclosing control to restore service after faults, improving system reliability. The SEL-551 family includes configurable time-overcurrent elements (such as 51P1T and 51P2T) and torque-control options (51P2TC) to tailor the response to specific fault scenarios, and it can be powered from a 125 VAC or DC supply. Panel-mount variants are available within the SEL-551/SEL-551C family for straightforward integration into existing switchgear. Typical applications include feeder and line protection in substations, transformer protection schemes, and protection for distributed electrical networks where coordinated reclosing reduces outage durations and protects critical assets.