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SEL releases TiDL technology — a simple, secure solution for digital substations

Engineered with simplicity in mind, TiDL saves copper, time, money, and lives

PULLMAN, Wash. — Schweitzer Engineering Laboratories (SEL) has added Time-Domain Link (TiDL) technology, an innovative substation solution that digitizes analog signals, to its SEL-400 series relay product line.

The TiDL solution replaces copper cables with fiber-optic cables. It is cybersecure and simple to apply, with no network engineering and no external time reference required. Because of the nonroutable protocol, the direct fiber connection between field modules and the relay in the control house, there’s no need for switches or routers.

In a TiDL implementation, SEL-2240 Axion devices are located close to the primary equipment in the substation yard and act as field modules. TiDL’s simple point-to-point architecture transports the data over fiber-optic cable to a TiDL-enabled SEL-400 series relay in the control house.

The Axion’s 24 kHz sampling rate improves the accuracy of metering and frequency tracking, and its modular architecture allows the user to select analog input, digital input and digital output modules to match the application. Relay settings remain the same as those in current SEL-400 series models, providing consistency and simplicity.

“With TiDL, you can achieve your digital substation needs in the simplest way possible,” said Joe Casebolt, SEL director of quality. “One of the ways we reduce complexity is by using point-to-point connections. No switches, zero network configurations, no settings for the field modules and the same protection algorithms and schemes that a user of a 400 series is already familiar with. You literally plug in the [fiber] cables, and it begins working.”

TiDL improves safety by removing high-energy cables from the control house where personnel typically work. Replacing copper cabling with fiber-optic cables reduces the costs and time associated with copper wiring installation, commissioning and documentation.

To learn more about TiDL technology, 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.