SEL & RTDS Technologies inventing the future of power system protection!

SEL & RTDS Technologies inventing the future of power system protection!

RTDS and SEL Mark Historic Milestone in Power System Protection

On May 7, 2018, the Public Service Company of New Mexico (PNM) energized a 345 kV series-compensated transmission line protected by SEL-T400L Time-Domain Line Protection devices with the trip circuits live to the breakers. This marked the first time that a relay based on traveling-wave protection principles was applied to protect a high-voltage transmission line, an event made possible by the new Traveling Wave Relay Testing (TWRT) capability in the RTDS® Simulator.

This event was the culmination of PNM’s plan to divide a 345 kV series-compensated transmission line into two segments intersecting at a new switching station. Because the division would result in overcompensation on the first section of the line, PNM reached out to Schweitzer Engineering Laboratories (SEL) for assistance in developing a protection design, calculating relay settings, and performing real-time digital simulation. This became the perfect opportunity to introduce PNM to the SEL-T400L.


“We used the RTDS Simulator’s TWRT capability for acceptance testing of the SEL-T400L to demonstrate the performance and behavior of the traveling-wave functions. The test results gave the customer the confidence to deploy the relay with direct tripping.”

Jordan Bell
SEL Protection Engineer


Two months prior to the energization of the line, engineers at SEL performed Model Power System Testing of both line segments using the RTDS Simulator at their testing facility in Pullman, Washington. SEL performed traditional testing at a timestep of 50 microseconds to test and prove the time-domain elements of the SEL-T400L. While the time-domain elements worked as expected, the testing of traveling-wave functions required an even faster timestep.

SEL-T400L-relayTo solve this dilemma with perfect timing, RTDS Technologies provided NovaCor™ simulation hardware with the recently announced TWRT capability. TWRT allowed SEL to test the traveling-wave directional and differential elements in real time to prove their performance to PNM.

The TWRT testing revealed an unprecedented operation time of 600 microseconds for the traveling-wave differential element for a midline single-phase fault. Moreover, the traveling-wave fault locator reported the fault location to within 0.02 miles on a 33.1-mile line! These testing results gave PNM the confidence to deploy the SEL-T400L with direct tripping.

This is only the beginning for traveling-wave protection devices and their associated test equipment. SEL Engineering Services and RTDS Technologies are at the forefront, inventing the future of power system protection. Learn more about how TWRT from RTDS and the SEL-T400L can improve your protection system.

By Jordan Bell, Schweitzer Engineering Laboratories
Appears in RTDS News, June 2018.