What Utilities Can Learn From Winter Storm Fern

Winter Storm Fern now holds the awfully unpleasant distinction of being the second-deadliest winter storm in U.S. history. From January 23-27, the massive (in scale and impact) weather event laid waste to electric infrastructure across the Southeast United States, knocking out power to millions of customers and claiming at least 172 lives, second only to Winter Storm Uri (246-290, depending on the source), which ravaged Texas in February 2021.

“Homes and businesses in Louisiana, Mississippi, Tennessee, and elsewhere endured a week or more without electricity, and many people were put in life-threatening situations,” observed Daniel Bresette, president of the Environmental and Energy Study Institute (EESI) in Washington, D.C.

Although service is now more or less restored to a pre-Fern-state, the storm remains a hot topic of discussion in the communities it affected, as utilities assess their response and rebuild a more resilient system in its wake.

Nashville Sparks Storm Investigation

Fern was the most devastating storm in Nashville Electric Service (NES) history, knocking out power to 230,000 customers at its peak. Around 800 poles were broken, along with trees and branches on power lines.

The City of Nashville recently formed a nine-person Winter Storm Response Commission, tasked with evaluating how the city handled Fern, in particular, Nashville Electric Service’s response. The group is required to issue its initial findings within six months and to make policy recommendations within a year.

“We did not meet the expectations of our customers through this storm,” NES CEO Teresa Broyles-Aplin said Monday in a report to the commission. “Through this storm, we did not provide the level of service and communications that our customers have come to expect from NES. We’ve historically had really good reliability. We’ve improved communications over the years. We were unable to deliver that through this storm.”

NES was inundated by customer communication during the event, citing 11 million+ views of its outage map, 2.3 million text messages, and 83,000 calls. Many in the service territory waited days for restoration; by the morning of January 29, more than 90,000 NES customers were still waiting for their lights (and heat) to come back on.

Entergy’s Assessment, Mississippi Damages

Many Entergy Louisiana customers were similarly frustrated by Fern. By midday on January 28, approximately 65,000 of the utility’s subscribers remained without power, down from a peak of 91,500 outages. By that time, crews had already discovered more than 700 damaged poles, 2,300 spans of wire, and 170 transformers in need of repair or replacement. On February 5, Entergy Louisiana reported it had finally restored service to the more than 130,000 customers who lost power during the event.

“This storm presented unique challenges, but we’re grateful to have every customer restored and are applying lessons learned to strengthen our response for future events,” reflected Phillip May, Entergy Louisiana president and CEO.

May credited the hard work of 4.400 line workers who worked long hours in hazardous conditions, climbing ice-covered poles, battling high winds, repairing damaged equipment in subfreezing temperatures, and returning to the same locations multiple times as conditions worsened. Tens of thousands of men and women contributed to service restoration across a multi-state, multi-utility, multi-week effort. Electric cooperatives from Tennessee, Arkansas, Florida, Kentucky, and Georgia answered the mutual aid call to help rebuild infrastructure and restore power. 

The Tennessee Electric Cooperative Association estimates more than 85,000 of its customers were impacted by Fern. Senator Scott DeLano (R-Biloxi) believes damages in Mississippi from Winter Storm Fern will ly exceed $400 million. At least 26 Mississippians were killed, and tens of thousands went without power for days, some for weeks.

What We Can Learn from Fern

A recent EESI analysis of Fern’s impacts highlighted common pain points for power generation and transmission systems during winter storms. They include:

• Icing of equipment power lines and towers leading to mechanical risk
• Automatic trips of breakers and potential forced shutdown of transmission lines or service stations
• Oil lubrication or thickening issues, plus cooling water blockages and fire suppression system shutdowns
• Decreased solar and wind generation (dark skies; ice/snow on panels and turbines)

Fern toppled more than two dozen transmission lines owned by Tennessee Valley Authority (TVA) that feed power to small utilities across Mississippi, Tennessee, and Louisiana, and iced over others. But fixing high-voltage lines would solve only part of the problem.

“We cannot forget about physical access to the assets to be repaired,” reminded Carlos Gamarra, vice president of energy, air, and IT at the Houston Advanced Research Center. “We are talking about miles and miles and miles of transmission lines, and accessing some of the problematic spots might not be easy when we are facing a week-long winter storm with temperatures below zero.”

Access in rural areas indeed slowed restoration during Fern. While many media focused on the highly-publicized NES and Entergy outage totals, tens of thousands of Mississippi co-op customers were also waiting for the lights to come back on.

Comparing Fern to Uri

The only Winter Storm in U.S. history that can hold a candle to Fern is 2021’s Winter Storm Uri. And it’s frankly more a flamethrower, but comparing the two deadliest storms and their aftermath can be a useful exercise.

Service outages: Gamarra estimates 10 million people lost power during Uri; 4.5 million alone in Texas. Some were without electricity for more than a week. Fern’s impact wasn’t as widespread, ultimately leaving between 1 and 2 million people in the dark for some duration. Water main breaks significantly hampered recovery efforts after Uri; they were not as big an issue with Fern.

Load shedding: Uri was the largest-scale load shedding event in the history of the U.S. grid. More than 20 gigawatts (GW) of load shedding and rolling outages persisted for days. Fern saw limited large-scale controlled load shed, but mostly storm-related outages. Uri forced 62 GW off-peak; Fern 5-10 GW. By February 16, 2021, as the ERCOT grid began to stabilize, there were still about 4.8 million power outages across Texas; 27% of the state.

Pricing imbalances: Winter Storm Uri famously ballooned ERCOT’s price cap to $9000 per megawatt-hour (MWh) for days, creating extreme wholesale market volatility.

“For example, residential customers had a utility fee linked to the wholesale market, paying something $10,000 to $16,000 a month for electricity,” recalled Gamarra. “That was created by the high demand and low capacity to provide that demand, low supply.”

Winter Storm Fern saw prices spike to around $1,800/MWh. Not great, but not nearly as bad. Some of that had to do with keeping more natural gas supply available than during Uri.

Customer cost: Uri’s total financial impact is estimated to be in the $100-130 billion range. The first back-of-the-napkin math on Fern suggests totals in the low tens of billions.

“Usually, those costs are assumed by the customers through long-term bonds added to their bills by the utility companies,” suggested the Houston Advanced Research Center’s Gamarra.

Around $10 billion in repair costs were passed on to customers ing Uri, including $1.2 billion approved by the Texas Public Utilities Commission in October of last year to cover repairs in the Houston area. No similar estimates are available for Fern yet, but Gamarra expects affected utilities will take a similar approach.

Opportunities to Improve

Winter Storm Uri prompted a suite of changes to electric policy and practice in Texas to curb the blow of the next “big one.” They ranged from mandatory weatherization standards and modifications to power markets to the addition of utility-scale battery storage and the Real-Time Co-Optimization Plus (RTC+) initiative to improve market operations.

According to Gamarra, there’s a greater emphasis on operational reserve requirements during winter and demand flexibility requirements for large energy consumers post-Uri. In EESI’s recent briefing on Fern, he highlighted the role of natural gas storage in maintaining supply and stabilizing prices during such winter storms. Storing natural gas in strategic locations can also help make energy markets more resilient.

“Another mechanism at the system operator level is the demand flexibility and the interconnection standards for large energy consumers,” noted Gamarra, citing the Texas Power Backup Program and freshly-approved Senate Bill 6, a standard defining new interconnection processes for large load customers over 75 megawatts (MW). “It includes demand flexibility requirements, meaning that on demand, these large energy consumers might curtail their consumption or shed or shift some load to help support the operations of the system.”

At the utility level, Gamarra recommends building and maintaining distribution-level assets with resilience in mind, meaning developing distribution systems and looping them instead of keeping them radial. He thinks it’s essential to encourage flexibility for industrial, commercial, and even residential end users with demand response programs.

“It’s also important to protect and prioritize critical infrastructure circuits near water infrastructure or hospitals, and support the deployment of microgrids at critical facilities,” he added.

“I don’t think there is a silver bullet when it comes to resilience,” Gamarra concluded. “I think all technologies have a role to play in the daily operations of power systems.”