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Time-Domain Line Protection

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Time-Domain Protection Products

Time-domain line protection sets a new standard for transmission line protection. With or without communications, it provides ultra-high-speed trip times, superior security, and simplicity.

The heart of time-domain protection architecture is a traveling-wave differential element (TW87) over a dedicated point-to-point fiber channel. This is combined with three other protection elements in the relay to provide comprehensive, secure transmission line protection.

Our time-domain products include MHz sampling that gathers detailed information about fault events, enabling SEL time-domain protection to register system conditions that other methods simply cannot see. This is why it’s able to make secure tripping decisions with unprecedented speed—5 milliseconds or less. And even the smallest fraction of time can make a large cumulative difference in preventing damage and wear to transformers, cables, and circuit breakers under fault conditions.

Nothing else can match the accuracy, speed, and security of a time-domain protection system.

Deployed together, the SEL-T401L Ultra-High-Speed Line Relay with time-domain protection and the SEL-411L Advanced Line Differential Protection, Automation, and Control System provide a complete transmission line protection solution.


SEL-T401L Ultra-High-Speed Line Relay

An evolution of SEL’s groundbreaking SEL-T400L Time-Domain Line Protection relay, this is a high-performance line protection relay with a complete suite of primary and backup protection functions.

  • Secure, ultra-fast tripping decisions with incremental-quantity and traveling-wave protection elements that work together.
  • Protection and supervisory functions, including sensitive directional, switch-onto-fault, overcurrent, over- and undervoltage, load encroachment, out-of-step tripping, and power swing blocking elements.
  • Traveling-wave fault location that pinpoints faults to the nearest tower span.

SEL-T400L Time-Domain Line Protection

Improve the reliability of your line protection with the high-speed operation and increased fault location accuracy of the SEL-T400L.

  • Secure tripping—ultra-fast reaction times to cover the gaps in traditional protection without overtripping.
  • Fault location—traveling-wave fault location pinpoints faults to the nearest tower span.
  • Monitoring and control—record and analyze traveling waves from faults, switching events, breaker restrikes, and self-extinguishing faults.
  • Protection upgrades—simple settings, a convenient 3U chassis, and SEL configuration and integration tools make it easy to replace existing relays.

SEL-2730M Managed 24-Port Ethernet Switch

Ethernet connectivity and secure network management for SCADA, engineering access, and control. Deploy the SEL-2730M with the SEL-T400L or SEL-T401L to integrate with your substation Ethernet network.


SEL ICON Integrated Communications Optical Network

A wide-area networking multiplexer optimized for utility and industrial applications. The ICON is configurable for SONET or Ethernet transport. It is also ideal for migrating legacy network technologies to a converged network solution. Deploy the ICON with the SEL-T400L or SEL-T401L to implement double-ended traveling-wave fault location over a multiplexed network.


SEL-2488 Satellite-Synchronized Network Clock

Receive Global Navigation Satellite System (GNSS) time signals, and distribute precise time via multiple output protocols, including IRIG-B and the Network Time Protocol (NTP).

Products and Service You Can Rely On

SEL products are designed and manufactured for the world’s most challenging environments, exceeding all industry standards for temperature, shock, and electric stress. An optional conformal coating for circuit boards adds an extra level of protection against contaminants in extreme environments.

Every SEL product comes with a ten-year warranty—the best in the industry. If any product fails under warranty, we’ll repair or replace it for free.

Questions? Contact Us!

We’re happy to answer all your questions and help develop the best solution for your needs.

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Unbeatable Support

SEL support teams are stationed in regional offices around the world and staffed with application engineers who are experts in our products and in power system applications.

Technical support for SEL-manufactured devices is always free. No matter how often you need to call or how long your SEL products have been in service, you’ll reach an SEL expert who can provide the service and support you need.

Our cybersecurity team is always ready with the information and resources needed to keep your OT networks and critical systems secure and working effectively. Cyber services support contracts can include incident response, audits, system hardening, and more, depending on your anticipated needs.