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Traveling-Wave Fault Location

SEL offers the only protective relays that include a traveling-wave-based fault locator, which is accurate to within a single tower span.

Traveling Wave hero

Field-proven SEL traveling-wave fault-locating technology calculates fault locations by measuring the arrival times of the naturally occurring traveling waves caused by a transmission line fault.

This provides much greater accuracy than traditional impedance-based methods.

On a 300 km line, for example, impedance-based fault locating (typically accurate to about 2 percent of the line length) would require the visual inspection of approximately 6 km of the line. Traveling-wave-based fault locating in SEL relays can estimate the fault location to within 300 m (1,000 ft), independent of the line length—about one tower span for the typical overhead transmission line.

Locate Transmission Line Faults Quickly and Accurately

There are two distinct methods that can be used for traveling-wave fault locating:

  • Single-ended, for applications without a communications channel.
  • Double-ended, which requires two relays with communications.

SEL relays with traveling-wave fault locating also include a backup impedance-based fault locator to ensure dependable fault locating in the widest possible range of operating conditions and fault types.

Single-Ended Traveling-Wave Fault Locating

The single-ended traveling-wave method uses a single relay to identify the first traveling wave and several successive traveling-wave reflections. It then calculates a prioritized list of possible fault locations.

This method is useful in applications without relay-to-relay communications or when your communications channel is down.

Double-Ended Traveling-Wave Fault Locating

The double-ended traveling-wave method precisely measures the first traveling-wave arrival times at both line terminals and uses time synchronization between the two relays to calculate the fault location.

Double-ended traveling-wave fault locating can be applied to two-terminal lines, including overhead lines, cable lines, and hybrid lines with a combination of overhead and cable sections. On series-compensated lines, the double-ended traveling-wave method provides more accurate results than the single-ended method.

When applied to hybrid lines with overhead and cable sections, the double-ended traveling-wave fault locating in the SEL-T400L Time-Domain Line Protection and SEL-T401L Ultra-High-Speed Line Relay compensates for line nonhomogeneity, improving the accuracy of the results. The fault location is made available to the relay’s adaptive autoreclose cancel (ARC) logic in less than 60 ms and is then compared with user-defined settings to either block or allow reclosing.

You can apply SEL relays with traveling-wave fault locating to multiterminal lines by obtaining the time stamps of the traveling waves that arrive at each end and using them in custom calculations in your SCADA/HMI software.

Improve System Reliability and Safety

The superior speed and accuracy of traveling-wave methods can facilitate advanced control functions that reduce the time and cost of repairs, mitigate potential property damage, and improve the safety of utility personnel and the public.

Control Autoreclosing on Hybrid Lines

SEL traveling-wave fault locators provide the fault type and an accurate fault location within milliseconds, which facilitates adaptive control of autoreclosing.

Use double-ended traveling-wave locating with ARC logic to:

  • Adaptively control autoreclosing and single-pole tripping by asserting a control bit based on the fault location obtained at the line terminals.
  • Allow single-pole tripping and reclosing for faults on overhead line sections.
  • Force three-pole tripping and inhibit autoreclosing for faults on cable sections.

Implement Line Monitoring for Condition-Based Maintenance

SEL relays with the line-monitoring function allow you to obtain a location-tabulated event count to keep track of low-energy activity and faults along the line.

Having identified problem locations based on event counts from the line-monitoring feature, you can prevent faults by selectively cleaning or replacing insulators, trimming vegetation, improving conductor antigalloping solutions, applying line spacers, or improving lightning protection.

Analyze Ultra-High-Resolution Transient Recordings

The SEL-T400L and SEL-T401L relays include ultra-high-resolution transient recording that captures current and voltage data at a 1 MHz sampling rate.

With SEL-5601-2 synchroWAVe Event Software, you can download the current and voltage data to visualize the timing of the initial and reflected traveling waves in a Bewley diagram and confirm the fault location.

You can also use the recording function to analyze high-frequency transients from line energizations, switching events, circuit breaker restrikes (or reignitions), and self-extinguishing faults.

Traveling-Wave Fault Locating Products


SEL-T401L Ultra-High-Speed Line Relay

The SEL-T401L delivers subcycle operating times and includes a complete suite of primary and backup line protection functions, plus line monitoring, high-resolution event reporting, and traveling-wave fault locating that pinpoints faults to the nearest tower span.

  • Single-ended and double-ended traveling-wave fault locating.
  • Advanced distance elements, dependable and sensitive directional elements, and overcurrent elements for a complete protection solution.
  • Traveling-wave fault locating that allows adaptive autoreclosing to better protect hybrid lines.
  • Monitoring and control features to allow for recording and analyzing faults and system events, such as switching, breaker reignition, and self-extinguishing faults.
T400L Left Front

SEL-T400L Time-Domain Line Protection

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

  • Secure tripping with ultra-fast reaction times to cover the gaps in traditional protection—without overtripping.
  • Fault locating—traveling-wave fault locating 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-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.


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 locating 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.

SEL Solutions in Action


Commonwealth Edison Company, Illinois, USA

Commonwealth Edison (ComEd) dispatched a crew directly to the faulted tower span. They discovered a buildup of avian excrement on a tower exactly 49.47 mi (79.61 km) from the relay terminal—328 m from the calculated location in the same tower span.


Salt River Project Power and Water, Arizona, USA

The fault source was found only 111 ft (33.8 m) from the calculated location. The line crew found the melted remains of a foil balloon on the C-phase insulator, which was mounted on a wood pole. The melting balloon material had caused a flashover across the insulator to the bare ground conductor.

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