Relay Keeps The Lights On

Designed to help ultility providers push there systems harder, the SEL-421 relay combines distance and directional protection with complete control for two breakers. Breaker-and-a-half and ring-bus configurations are accommodated, with the component containing all the necessary protective elements and control logic to protect overhead transmission lines, both uncompensated and series-compensated, and underground cables.Automation features include 32 programmable elements each for local and remote control and 64 programmable elements for latch control. The relay transmits metering data, protection-element status, and contact I/O status via UCA and DNP protocols. And a dual-breaker monitor gives comparisons between the last and average mechanical and electrical tripping times.