FERC today invited the public to comment on a potential framework that would make more efficient and cost-effective use of the power grid by requiring the application of dynamic line ratings (DLR), which use up-to-date forecasts of weather conditions to improve the accuracy and transparency of transmission line ratings.
Transmission line ratings represent the maximum transfer capability of each transmission line and can change based on weather conditions. Today’s Advance Notice of Proposed Rulemaking (ANOPR) comes just weeks after the Commission issued its landmark long-term transmission planning rule, Order No. 1920, which outlines how to plan and pay for facilities needed to power the economy through the 21st Century.
“Our success in ensuring reliability and operability of our nation’s transmission grid requires work on many fronts,” FERC Chairman Willie Phillips said. “Last month, we took the major step of issuing Order No. 1920 to determine how to plan and pay for transmission facilities that our nation will need. Today, we are looking to wring efficiencies out of the grid so we can make the best and most efficient use of what we already have.”
The ANOPR reflects public comments in response to the Commission’s Feb. 17, 2022, Notice of Inquiry on dynamic line ratings. The Notice of Inquiry, in turn, was built on the Commission’s December 2021 rulemaking, Order No. 881, which required transmission line ratings to reflect ambient air temperatures to improve efficiency in operating transmission lines.
Comments are due within 90 days of the ANOPR being published in the Federal Register. Reply comments are due within 120 days of the ANOPR being published in the Federal Register.
About Dynamic Line Ratings
Dynamic Line Ratings (DLR) use up-to-date weather forecasts to improve the accuracy and transparency of transmission line ratings. Transmission line ratings represent the maximum transfer capability of each transmission line and can change based on weather conditions.
- Weather conditions that cool transmission lines can increase a transmission line’s transfer capability; weather conditions that heat transmission lines can reduce transfer capability.
- Solar conditions, including solar heating and cloud cover, and wind conditions, including wind speed and direction, affect transfer capability by heating or cooling transmission lines. Increased cloud cover and increased wind speeds across transmission lines can cool the lines and increase their transfer capability while still maintaining safe and reliable grid operations.
The ANOPR seeks comment on several matters:
- Whether to reflect hourly solar conditions in all transmission line ratings, and how to determine which transmission lines would benefit from ratings that reflect hourly wind conditions.
- Regarding wind conditions, how transmission congestion levels and environmental factors could identify the locations of transmission lines that would benefit the most.
- Other technical details of transmission line ratings that reflect wind conditions, including weather forecasts and sensors.
The ANOPR considers a framework that outlines potential solar and wind requirements for transmission line ratings.
- Solar conditions: Transmission providers would be required to reflect more detailed solar heating forecasts in all transmission lines’ ratings.
- Wind conditions: Transmission providers would review their own transmission congestion patterns to identify any highly congested transmission lines located in windy areas.
- Transmission providers would be required to reflect forecasts of wind speed and direction in their lines’ ratings.
- The ANOPR also seeks comments on new methods to measure congestion for transmission line and related data reporting requirements.
Further considerations:
- Reflecting hourly solar conditions in transmission line ratings has the potential to benefit all transmission lines and does not require installation of sensors or other costly equipment. This would go beyond the simple day/night considerations in Order No. 881 by requiring hourly forecasts of solar intensity and cloud cover events.
- Wind conditions have an even higher potential for line cooling than solar conditions, as wind influences line cooling more than any other single weather factor. However, reflecting wind conditions in transmission line ratings can cost more per line because it may require installation of sensors and communication equipment.
- Recognizing this potential added cost, the ANOPR specifies that transmission providers could be required to reflect wind conditions in ratings only on lines that both are heavily congested and located in geographic areas with windy conditions.
