Line Current Differential Protection—Protect two-terminal transmission and subtransmission lines with the same ratio CTs on each end. Apply a 64 kbps digital communications channel for complete phase and ground fault protection with simple settings.

Simple Installation—Set the relay in minutes! Only label the relay and terminals, and provide a unique address for the transmit and receive communications. Connect single-mode optical fiber, 1300 nm and 1550 nm, for distances up to 120 km (74 mi) without a repeater. No additional transceivers are required.

Differential Communications—Apply the SEL-387L Line Current Differential Relay with a multiplexed communications system using single-mode fiber optics or the built-in IEEE C37.94 compliant connection. Connect to EIA-422 and G.703 multiplexers by using the SEL-3094 Interface Converter.

Three-Terminal and Tapped Lines—Protect three-terminal lines with two SEL-387L Relays and one SEL-311L Line Current Differential System. Coordinate the tapped load protection for sensitivity and speed by designating the SEL-311L as the leader to make all the protection decisions. No settings are made in the SEL-387L Relays.

Simple Backup Protection—Choose the SEL-387L as a simple solution for discrete backup protection. Coordinate with another local relay, such as an SEL-551 Overcurrent/Reclosing Relay, to provide breaker failure, autoreclose, overcurrent, and ground fault protection functions in addition to current differential protection.