PNM's standardization on ultra-high-speed line relays to protect their EHV transmission network

Session Title: Transmission networks (including EHV and UHV)
Chair: Richard Adams

Public Service Company of New Mexico’s (PNM’s) commitment to produce 100 percent carbon-free energy by 2040 has spurred the growth of renewable energy resources in their electric grid, increasing the penetration of inverter-based resources (IBRs) into the system. IBRs provide additional load support and improve PNM’s renewable energy portfolio. However, IBRs also pose many challenges to PNM’s existing extra-high voltage (EHV) transmission line protection system. These challenges include low fault current contributions, reduced system inertia, and nontraditional fault waveform signatures. As more IBRs are introduced into the electric grid, there becomes a greater need to modernize the protection system to overcome these challenges. This paper will discuss the protection solution adopted by PNM for applications with high penetration of IBRs.

With the goal of modernizing the line protection technology and the need for system-wide consistency, PNM standardized their EHV transmission line protection using ultra-high-speed (UHS) line relays that provide fast and dependable protection by using both phasor and time-domain principles. The standardization allowed PNM to create a new line protection philosophy that includes single-pole tripping and reclosing, a new panel design, and an updated breaker failure scheme. The new protection standard employs best-known practices and innovative methods for designing, testing, and commissioning a protection system using UHS relays.

This paper discusses PNM’s EHV transmission line protection standard and the application of the standard to one of six 345 kV transmission lines where PNM has successfully installed this new line protection. This paper also discusses the validation testing of the protection scheme using hardware-in-the-loop simulation with a Real-Time Digital Simulator (RTDS). Onsite commissioning, end-to-end testing, and lessons learned are also discussed.