html{display:none} Distance Protection Solutions | Schweitzer Engineering Laboratories

Distance Protection

Distance Protection hero

SEL provides reliable and secure distance protection that can be applied with or without communications and can function as a backup for communications-dependent line current differential protection.

Distance protection solutions include:

  • Quadrilateral and mho distance elements—SEL transmission relays allow you to choose either or both.
  • Optimized system loading—Built-in load encroachment logic allows you to securely apply distance protection elements on heavily loaded transmission lines.
  • Improved system stability—The SEL zero-setting out-of-step (OOS) blocking function improves security during power swings without requiring time-consuming and expensive system stability studies.
  • Communications-assisted tripping—SEL transmission protection relays accommodate many of the common pilot protection schemes, so you can configure protection without any need for external coordination devices.

SEL-T401L Ultra-High-Speed Line Relay

An evolution of SEL’s groundbreaking SEL-T400L Time-Domain Line Protection relay with time-domain protection technology, the SEL-T401L includes a complete suite of primary and backup protection functions.


SEL-421 Protection, Automation, and Control System

High-speed distance and directional protection plus complete control of a two-breaker bay.


SEL-311C Transmission Protection System

Distance protection, monitoring, and reclosing for transmission lines.

Communications-Assisted Protection

Implement communications-assisted tripping and remedial action schemes (RASs) with SEL networking and control products.


SEL ICON Integrated Communications Optical Network

A wide-area networking multiplexer optimized for utility applications. The ICON is configurable for SONET or Ethernet transport. It is also ideal for migrating legacy network technologies to a converged network solution.


SEL-3555 Real-Time Automation Controller (RTAC)

Our most powerful automation controller—ideal for automation and integration of protection systems, both large and small.


SEL-2730M Managed 24-Port Ethernet Switch

Ethernet connectivity and secure network management for SCADA, engineering access, and control.

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.

Contact Engineering Services


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.