html{display:none} SEL-T401L Ultra-High-Speed Line Relay | Schweitzer Engineering Laboratories


Ultra-High-Speed Line Relay

The SEL-T401L is a high-performance, easy-to-use line protective relay in a 3U package. Built on the field experience of the SEL-T400L Time-Domain Line Protection, the SEL-T401L delivers unprecedented operating times and includes the complete suite of primary and backup protection functions that you expect in a line protection system. Suitable for a wide range of applications, the SEL-T401L offers an opportunity to reset the complexity of line protection applications with its simple protection philosophies, and reduced settings count.

You can apply the SEL-T401L on its own or as part of a redundant protection system with other SEL relays without concerns for common-mode failures. The new technology of traveling waves and incremental quantities along with the enhancements and simplifications in phasor-based protection elements make the SEL-T401L protection philosophy, hardware, and software different from other SEL line protective relays. You’ll gain efficiency by using common SEL configuration and integration tools and also benefit from strong diversity in hardware, software, and protection operating principles.

Starting At

$15,000 USD

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Ultra-High-Speed Protection— The SEL-T401L offers the complete suite of protection functions that you expect in a line protection system. Protect your lines by using the SEL-T401L ultra-high-speed elements and schemes based on the field-proven SEL time-domain technology of traveling waves and incremental quantities with demonstrated operating times on the order of 1–5 ms. The SEL-T401L includes high-performance distance protection with five zones of phase and ground elements, individually selectable as either mho or quadrilateral, with subcycle operating times. The SEL-T401L also includes dependable protection and supervisory functions, including sensitive directional, switch-onto-fault, overcurrent, over- and undervoltage, load encroachment, out-of-step tripping, and power-swing blocking.

Unparalleled Fault Locating— The SEL-T401L includes single- and double-ended traveling-wave-based fault-locating methods that are accurate to within a single tower span. It also includes single- and double-ended impedance-based methods. The combination of single-ended and double-ended methods, as well as traveling-wave-based and impedance-based methods, provides the best accuracy and dependability for any combination of operating conditions and fault types. Combining the SEL-T401L high-speed double-ended traveling-wave-based fault-locating technology and built-in adaptive location-dependent autoreclose cancel logic allows selective reclosing on the overhead portion of hybrid lines and inhibits reclosing on cable portions. The SEL-T401L also includes a line monitor function, which can be used for condition-based line maintenance to prevent line faults and to discover weak spots along the line.

Simplicity— Reset the complexity of your line protection applications with the simple and robust protection philosophies and considerably lower settings count of the SEL-T401L. The SEL-T401L design achieves the right balance between flexibility and simplicity. We have streamlined, named, grouped, and presented the relay settings with great care for intuitive application and ease of use. Apply the relay with preconfigured logic, or adjust the factory defaults with SELogic equations using gates, timers, and latches.

Ultra-High-Resolution Transient Recording— The SEL-T401L measures and records line currents and voltages with high-fidelity (1 MHz, 18-bit) sampling, offering an enhanced understanding of the events on your power system. This allows you to analyze high-frequency transients, such as traveling waves from faults, switching events, breaker restrikes, and self-extinguishing faults.


    1. 1

      USB 2.0 port for local engineering access

    2. 2

      Display for viewing metering, event, fault location, and relay status information

    3. 3

      Simple HMI navigation

    4. 4

      Slide-in label pocket and LED targets for viewing trip cause, fault type, and basic relay status

    5. 5

      Large slide-in label pocket for diagrams or asset information

    1. 1

      Six trip-rated high-speed outputs for single-pole tripping of two breakers

    2. 2

      Alarm output

    3. 3

      Five inputs with a common terminal

    4. 4

      IRIG-B time input

    5. 5

      Three fiber-optic ports for multiplexed or direct protection signaling (SEL MB8 or IEEE C37.94)

    6. 6

      100 Mbps or 1 Gbps small form-factor pluggable (SFP) Ethernet port for engineering access and SCADA

    7. 7

      SFP fiber-optic port for ultra-high-bandwidth protection signaling over direct fiber

    8. 8

      Eight outputs for POTT, DCB, DTT, breaker failure initiation (BFI), and other signaling

    9. 9

      Eight inputs for POTT, DCB, DTT, triggering, and other signaling

    10. 10

      Breaker 1 and 2 current inputs

    11. 11

      Line voltage

    12. 12

      Auxiliary voltage (metering and digital fault recorder)

    13. 13

      Power supply



Minimum QuickSet Version


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Latest Firmware Versions

There are no firmware versions available for this product.

Product Revision Firmware ID Date Available Serial Number
SEL-T401L R101-V0 SEL-T401L-R101-V0-Z002001-D20210106 1/29/21 ~1210290001

The Firmware IDs for older versions of the firmware can typically be found in Appendix A of the instruction manual.

Minimum QuickSet Version

Instruction Manuals

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