SEL-421 Distance Relay
Apply the SEL-421 Protection, Automation, and Control System for high-speed distance and directional protection and complete control of a two-breaker bay.
Protect any transmission line using a combination of five zones of phase- and ground-distance and directional overcurrent elements. A graphical user interface system provides logic and application templates for typical line protection schemes. Patented Coupling Capacitance Voltage Transformer (CVT) transient overreach logic enhances the security of Zone 1 distance elements. Best Choice Ground Directional Element® logic optimizes directional element performance and eliminates many directional settings. Optional additional logic prevents Zone 1 overreach on series-compensated lines. Optional incremental components provide ultra-high-speed (subcycle) operation for application on critical lines requiring high-speed fault clearing.
Front- and Rear-Panel Diagrams
Select an SEL-421 Protection, Automation, and Control System with operating times to match your system requirements. Use standard-speed or subcycle elements for critical applications. Use Mirrored Bits® communications and high-speed outputs with all SEL-421 Relay models to improve operating times.
Integrate a two-breaker, four-shot recloser and SELogic® control equations into a complete automation system. Initiate reclosing based on fault type, protection zone, or external conditions.
View data across the system with 10 μs time-stamping accuracy. Verify load angles and system impedances with measured values.
Apply Ethernet (FTP, Telnet, DNP3 LAN/WAN, SNTP, and IEC 61850) connectivity to simplify and speed information distribution. Integrate expanded SELogic control equations into your complete station automation system.
Improve reliability with continuous checks of station batteries and relay health. Reduce costs through tailored maintenance intervals based on accumulated breaker duty and operating times. View relay read-only data, including settings, metering, event reports, relay status, and configuration, with built-in web server over Ethernet.