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SEL-411L provides high-speed 87L performance over Ethernet for four terminals

PULLMAN, Wash. — Schweitzer Engineering Laboratories, Inc. (SEL) recently released the new 87L-over-Ethernet feature in its SEL-411L Advanced Line Differential Protection, Automation, and Control System. The SEL-411L now supports data exchange over a dedicated Ethernet network to provide line current differential (87L) protection for transmission lines with as many as four terminals.

“In today’s power systems, multiterminal lines are increasingly common,” said Lee Underwood, R&D director of power system protection. “Line current differential protection is an ideal way to protect multiterminal lines. With the latest release of 87L protection using Ethernet communications in the SEL-411L, utilities can now provide high-speed protection for lines with up to four terminals, even with two breakers per terminal. Over serial communication, the SEL-411L can provide 87L protection for up to three terminals.”

The SEL-411L is a high-speed transmission line differential, distance and current protection relay that provides single- and three-pole tripping and reclosing with synchronism check, circuit breaker monitoring, breaker failure protection and series-compensated line protection logic. The relay features extensive metering and data recording, including high-resolution data capture and reporting. In addition, the SEL-411L supports in-line power transformer applications and compensates for line-charging current in 87L protection applications over long extra-high-voltage lines or cables.

The SEL-411L is the only advanced transmission line relay with an optional traveling wave fault location feature that can pinpoint the location of a fault within a tower span. Accurate fault location reduces costs by allowing line crews to spend less time finding faults and restore power to customers faster. The 87L-over-Ethernet functionality is available for order today at no additional cost. For more information on features, benefits and applications, visit

SEL serves the power industry worldwide through the design, manufacture, supply and support of products and services for power system protection, monitoring, control, automation, communications and metering. For more than 30 years, SEL has provided industry-leading performance in products and services, local technical support, a 10-year worldwide warranty and a commitment to making electric power safer, more reliable and more economical.