Two months after issuing a major power line ratings rule, the Federal Energy Regulatory Commission on Feb. 17 launched a related notice of inquiry into the costs and benefits of implementing capacity-enhancing dynamic line ratings.

The notice of inquiry follows a December 2021 final rule (RM20-16) that requires transmission operators across the U.S. to move away from seasonal or static line ratings in favor of ambient adjusted ratings, which use near-term forecast ambient air temperatures. Ambient adjusted ratings enable existing electric transmission lines to operate at a higher capacity factor than they otherwise would under seasonal or static line ratings.

In issuing the final rule, FERC stopped short of requiring the use of a more advanced technology — dynamic line ratings, or DLRs — and instead opened a new administrative proceeding (AD22-5) to explore the technical challenges and opportunities associated with the technology's widespread adoption.

DLRs, which rely on advanced sensors, are updated more frequently with real field data such as ambient air temperatures, wind speed, cloud cover, solar heating intensity, precipitation, and line tension or sag. The technology can boost a line's capacity by up to 40% in some wind-rich areas of the country.

A February 2021 report produced by the consulting firm The Brattle Group estimated that the nationwide deployment of DLRs, in combination with two other grid-enhancing technologies, could produce $5 billion in annual energy cost savings while cutting carbon emissions by 90 million tons per year.

The Feb. 17 notice of inquiry seeks additional information on whether a lack of DLR requirements renders wholesale electricity rates unjust and unreasonable. It also seeks comment on potential criteria for DLR requirements, costs and benefits, and potential time frames for requiring DLR implementation.

"I believe this is a critical step," Chairman Richard Glick said during FERC's monthly open meeting. "While we're focused on the increased demand for transmission capacity around the country, it is important that we also do what we can to better utilize existing transmission capacity."

On a call with reporters, Glick also noted that DLR technology can help alleviate clogged transmission interconnection queues as regional grid operators struggle to deal with a surge in renewable energy development. The PJM Interconnection LLC, for example, is proposing a two-year pause for processing new interconnection requests so that it can work through a backlog of about 2,500 projects, 95% of which are renewable resources.

"I do think that there's a strong linkage between potential use of DLRs and hopefully expediting the queue process," Glick said.

Unlocking dormant transmission capacity can reduce the need for interconnection customers to pay for costly network upgrades, the chairman said.

Glick added that the commission is assessing the benefits of DLRs through a broader advanced notice of proposed rulemaking (RM21-17) aimed at speeding electric transmission build-out.

The Feb. 17 notice of inquiry was cheered by LineVision Inc., a leading DLR company, as well as a trade group focused on grid-enhancing technologies.

"It's exciting to see FERC's action today essentially indicating that they're looking to build a record on how and why DLRs should be used going forward," Hilary Pearson, LineVision's head of government and regulatory affairs, said in an interview.

The WATT Coalition, which promotes grid-enhancing technologies, supports DLR deployment "wherever it makes sense," director Rob Gramlich said.

"The WATT Coalition looks forward to working with renewable energy developers to share their experiences with transmission constraints that could be solved with DLR, as well as transmission owners who've seen the benefits of DLR firsthand," Gramlich said in a statement.

Comments on the notice of inquiry are due 60 days after its publication in the Federal Register.