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Line Current Differential Protection

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SEL Line Current Differential Protection Products

SEL line current differential protection provides robust, configurable high-speed protection for transmission line systems where distance protection may be inadequate.

The advanced technology in SEL relays—with subcycle single- or three-pole protection, flexible communications, and backup distance protection—helps solve your most difficult and complex protection challenges, such as parallel line protection and maintaining primary line protection when connecting wind farms to the grid.


SEL-411L Advanced Line Differential Protection, Automation, and Control System

Complete protection and control of any transmission line in a single relay. The SEL-411L offers line current differential protection plus all the distance protection features of the SEL-421 Protection, Automation, and Bay Control System. Deploy the SEL-411L with the SEL ICON or other communications platforms.

  • Subcycle single- or three-pole line current differential protection.
  • Exceptionally sensitive and secure operation using phase- and sequence-based operating elements plus our patented generalized Alpha Plane technology.
  • Flexible 87L data channel selection—choose the communications channel that fits your application needs.
  • Line-charging current compensation for better protection of long extra-high-voltage lines.
  • Maintaining load balance and line protection with automatic out-of-step (OOS) blocking and tripping.
  • Traveling-wave fault location pinpoints faults within one tower span.

SEL-311L Line Current Differential Relay

Subcycle current differential protection with four-zone distance and directional overcurrent backup. Apply the SEL-311L on two- or three-terminal lines.

  • High-speed protection independent of line loading, CT saturation, or tapped load.
  • Integrated four-shot reclosing.
  • Single and dual differential channels for increased dependability and security.
  • Distance protection plus directional and nondirectional overcurrent elements to provide a full backup protection system.

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-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).

More Products for Transmission Line Protection

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.