FERC rule could boost wind energy across grid

Source: By Peter Behr, E&E News reporter • Posted: Monday, November 23, 2020

The Federal Energy Regulatory Commission proposed a rule last week that advocates say could boost wind energy, pack more power on selected high-voltage lines, improve grid reliability and lower costs.

FERC opened a 60-day comment period Thursday to consider a proposal to change how grid operators rate the capacity of interstate transmission lines. Under the plan, regional grid operators could use real-time information to bring more electricity onto their systems. And that could help wind power generators as weather patterns shift over the course of a day.

The extent to which grid operators should use high-performance computing and artificial intelligence to manage their systems has been an ongoing debate within the industry.

FERC’s initiative centers on two ways to increase power flows by fine-tuning power line capacity ratings — a much cheaper course than building new lines.

Because power lines are at less risk of overheating when temperatures are lower and the wind is blowing, weather forecasts are a key to setting line ratings. Grid operators typically use annual or seasonal forecasts, but FERC’s proposed rule would require regional grid operators to update forecasts at least hourly, creating what are called “ambient-adjusted ratings.”

A second, more dramatic proposed change would allow grid operators to experiment with much finer, faster updates called “dynamic line ratings,” or DLRs. This approach would use actual temperature readings and other data from sensors on transmission lines that are fed to operators’ computers to create day-ahead or real-time forecasts.

The potential plus for wind power deliveries is plain, said Rob Gramlich, president of Grid Strategies LLC, an advocate for DLRs.

Most U.S. line ratings are set conservatively based on annual or seasonal forecasts that plan for worst-case conditions, such as a 100-degree Fahrenheit day. When an abrupt weather change speeds up the wind velocity, and grid operators know that is happening, they can allow more current to flow from a wind farm into the grid, he said.

“The same wind that spins blades also cools lines, enabling more delivery,” Gramlich said.

Jay Caspary, vice president of Grid Strategies, said with DLRs, “we’d use sensors and technology to know what to expect, not guess.”

DLR technology is rarely used on the U.S. grid. The proposed rule would require regional grid operators to allow transmission owners to electronically update transmission line ratings on at least an hourly basis.

Engineering experts have told FERC staff that validation systems would be needed to convince transmission grid operators to trust real-time, automated decisions on power line capacity.

A FERC research paper notes that benefits from the new strategies are greatest on lines that are regularly congested, and vary with terrain and other factors.

Strong winds that cool an exposed ridge-top power line would do much less for another line shielded by forests on each side. But the potential is significant, according to several studies.

A trial by the New York Power Authority indicated DLRs could increase power flows by between 30% and 44%. Another test by Oncor Electric Delivery Co., Texas’ largest transmission and distribution electric utility, showed the dynamic line ratings increased the delivery of wind power and boosted transmission capacity overall.

As to costs, Potomac Economics, market monitor for the Midcontinent Independent System Operator grid region, estimated that use of ambient-adjusted ratings throughout MISO would have made operations more efficient, saving customers around $78 million in 2017 and $94 million in 2018 in congestion charges.

A divided industry

The power sector is divided on both approaches, FERC staff noted in the proposed rule.

While DLRs have unique benefits, agency staff noted that “they also have unique implementation challenges,” including physical and cybersecurity risks.

Sensors measuring local weather conditions and the sag in lines would have to be installed, maintained, and defended against vandals and hackers, FERC said.

In comments to FERC, MISO transmission owners said some regional grid operators are able to change line ratings “on the fly” using DLR data in their control rooms, but others would have to invest in updating multiple control systems.

In its comments to FERC, WATT, the advocacy organization Working for Advanced Transmission Technologies, acknowledged that “security can be a concern” but argued it “should not be used as a red herring to avoid FERC improvements to the grid’s reliability and efficiency.”

Dominion Energy Inc., in Richmond, Va., said dynamic line ratings offer only slight advantages to the less expensive and challenging ambient-adjusted ratings systems, but impose operating challenges and complexity.

American Electric Power Co., in Columbus, Ohio, said it has used ambient-adjusted ratings for real-time operations for more than a decade, pulling in separate temperature readings from zones in its region. Exelon Corp., in Chicago, explained that ambient-adjusted ratings are a cost-effective way to make transmission more efficient and less expensive for customers.

But St. Louis-based Ameren Corp., arguing for MISO transmission owners, said the industry isn’t ready for full implementation of either strategy. If FERC goes ahead with the rule, it should be tried in pilot projects first, Ameren said.

PacifiCorp, based in Portland, Ore., said benefits of implementing the two ratings systems would not materialize on all lines so should not be required everywhere.

FERC noted in the proposed rule that it was only proposing the use of ambient-adjusted ratings for certain near-term transmission deliveries with a one-year compliance deadline for congested lines. All other lines would have two years to comply.

Gramlich said in an email, “Making line ratings more dynamic is one tool to dramatically increase the capability of the existing network, quickly and cheaply. Utilities have looked at the strategies in the past.” But the response, Gramlich said, was, “Yeah, that works, but I don’t make money from it, so no thank you!”