FERC Seeks Input on Dynamic Line Rating Requirements to Maximize Use of the Existing Transmission Grid
Regulators at the Federal Energy Regulatory Commission (FERC) are exploring ways to safely maximize the use of the existing electric grid at the same time they see the need for substantial investments in the nation's transmission infrastructure.
On February 17, 2022, in an effort to improve the accuracy of electric transmission line ratings, FERC launched a notice of inquiry (NOI) seeking industry-wide comment on the implementation of dynamic line ratings (DLR). The NOI is designed to provide a record to support new DLR requirements for utilities that would allow for the delivery of more power on existing transmission lines.
A DLR determines a transmission line's real-time carrying capacity with the capability of reflecting in its determinations up-to-date weather forecasts including precipitation, cloud cover, and transmission line degradation conditions such as sag or tension. DLRs, through the use of advanced sensors, reduce congestion on power lines and optimize asset utilization, ultimately improving the efficiency of the line and in turn reducing costs for customers.
The NOI supplements Order No. 881, a new FERC rule issued in December 2021, which required transmission providers to use ambient-adjusted ratings (AAR). AARs factor in on an hourly basis near-term changes in temperature and solar heating, effectively allowing more power to move through electric lines than static or seasonal line ratings. Static and seasonal line ratings are typically only updated during equipment changes or when weather forecasts are revised, thus using overly conservative assumptions for setting line ratings that do not accurately represent the transfer capability of the system.
Unlike AARs however, DLR implementation presents a new set of challenges that include sensor purchases, installation, and maintenance, as well as a myriad of cybersecurity concerns. Nonetheless, FERC asserts that the use of DLRs "generally allows for greater power flows than would otherwise be allowed" and that their use "can also detect situations where power flows should be reduced to maintain safe and reliable operation and avoid unnecessary wear on transmission."1
The NOI seeks comment from the industry and interested stakeholders on:
- The need for DLR requirements to improve the accuracy of transmission line ratings;
- Whether DLRs should be required only when certain criteria are met;
- The benefits, costs, and challenges of implementing DLRs;
- How best to design DLR requirements; and
- Potential time frames for requiring DLR implementation.
Initial comments on the NOI will be due April 25, 2022, with reply comments due May 25, 2022.
* Taylor Sutton is a law clerk in the Washington, D.C. office of Davis Wright Tremaine.