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Time-domain and traveling-wave technologies are delivering dramatic reductions in transmission relay operating times. 

Recently, a large integrated power company in western India installed two SEL-T400L Time-Domain Line Protection Relays for performance monitoring on a high-voltage transmission line and saw them in action just four days later when they recorded their first fault. The TD21 distance element in the SEL-T400L operated in 8 milliseconds, and the TD32 directional element operated in only 2 milliseconds.

The next day, another fault struck. This time, the TD32 element operated in 1.35 milliseconds and the traveling-wave directional (TW32) element operated in a mere 60 microseconds. Two days later, a third fault was recorded. The Zone 1 underreaching TD21 element operated in 2.02 milliseconds, while the TD32 and TW32 directional elements operated in 1.22 milliseconds and 135 microseconds, respectively. Engineers at the company were blown away by the speed of this powerful technology.

SEL has made significant pioneering advances in recent years using traveling-wave protection and fault-locating methods in high-voltage power systems. Traveling-wave technology works by detecting the transients (traveling waves) that propagate along a transmission line at close to the speed of light following a fault. The SEL-T400L Relay exploits the capabilities of this technology to achieve response speeds that are impossible with conventional relays. This relay can also accurately locate faults to within one tower span and offers high-resolution event data recording capabilities.

In addition to ultra-high-speed fault detection, the SEL-T400L records event data with a 1 MHz sampling rate (i.e., 1 million samples per second). It can also store information on up to 50 events at a time with a duration of 1.2 seconds per event. This unprecedented quantity of extremely high-resolution fault data provides engineers new opportunities to understand and improve their systems. 

Learn more about what the powerful traveling-wave fault-locating technology in the SEL-T400L can do for your system.