Schweitzer Engineering Laboratories SEL-411L Relay

Schweitzer Engineering Laboratories’ SEL-411L Advanced Line Differential Protection, Automation, and Control System is a four-terminal protection relay for transmission lines that combines 87L line differential protection with distance and current protection in a single package. It enables fast, accurate protection and reclosing with synchronism check, and includes built-in circuit-breaker monitoring, breaker-failure protection, and series-compensated line protection logic to manage lines with compensation. The SEL-411L family includes standard hardware and the SEL-411L-2 SV variant for enhanced synchrophasor (SV) capabilities. Designed for diverse substation architectures, it supports configurations such as breaker-and-a-half, ring-bus, or double-bus double-breaker setups. Communications and time synchronization are robust, with support for IEC 61850 Edition 2.1, DNP3, SEL ASCII, SEL Fast Message, PRP, and PTPv2, enabling seamless SCADA integration, PMU data streaming, and precise timing across networks. An engineering-access port simplifies setup, configuration, and ongoing relay management, making the SEL-411L a compact, high-performance solution for protecting long transmission lines and coordinating protection in multi-terminal networks.