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.