The Tennessee Valley Authority earlier this month released a report that analyzed how TVA responded to Winter Storm Elliott in December 2022 and the actions it took to understand what happened and why and to draw lessons from the event.
“Winter Storm Elliott did not take TVA by surprise. TVA anticipated and prepared for this event, but the storm’s speed and intensity exceeded forecasts and TVA’s efforts,” the report noted.
TVA committed a significant amount of generation resources ahead of the event to meet predicted demand, and took additional measures such as:
- TVA’s generation plants took extra steps to ensure readiness;
- TVA’s External Relations team began outreach to customers and stakeholders; and
- TVA Police & Emergency Management engaged with TVA business units to remind them of the possibility of agency-level emergency coordination based on storm impact.
The high winds, heavy rain, and cold temperatures of Winter Storm Elliott arrived in the TVA service territory on December 22. These conditions increased energy demand beyond what had been forecast, resulting in the highest 24-hour electricity demand supplied in TVA history on December 23 as the speed, intensity, scale and duration of Winter Storm Elliott exceeded the design basis for some of TVA’s power plants, the report said.
In total, 38 of TVA’s 232 generating units were negatively impacted, mostly due to instrumentation that froze, the report said.
“TVA employees worked around the clock to increase generation to meet the demand, including dispatching units that had previously not been in service and executing day-ahead, real-time purchases and emergency purchases,” the report noted.
In addition, TVA employees worked in extreme weather conditions to keep generating units online and restore units impacted during the storm. This included placing additional temporary structures, insulation, and heaters around equipment at impacted units. As a result of their efforts, 14 of the 38 generating units lost were recovered and returned to service within 48 hours.
The storm also challenged neighboring utilities, limiting power availability, resulting in energy demand exceeding supply being generated and purchased. For the first time in TVA’s 90-year history, TVA was forced to implement emergency procedures directing local power companies to reduce power demand that resulted in localized interruptions in order to keep the overall system stable.
What TVA Learned
Following Winter Storm Elliott, TVA immediately took steps to understand what happened and why and to draw lessons from the event through initiating a formal After-Action Technical Review.
As part of this effort, TVA engaged industry experts and customers for input and feedback, incorporated independent oversight and expertise, and committed to share findings and progress as part of TVA’s commitment to transparency, the report noted.
TVA’s after-action reviews included a blue ribbon commission, an after-action technical team and a customer engagement team.
The review looked at five main categories or activities across the agency and the response of each to the storm: energy supply, real-time load forecasting and operations, emergency protocols, customer and stakeholder engagement and transmission.
A team was formed for each category to conduct a deep dive into what happened, how TVA responded, and how TVA can improve in the future.
Specifically, each team determined the specific events, or drivers, that led to load reduction during Winter Storm Elliott; considered improvement opportunities to support an enhanced response to future hazards; and documented strengths, which include actions taken that had positive outcomes and should be evaluated for future events.
Based on the teams’ findings, they also determined recommendations for potential changes to the approach or execution of TVA’s strategy.
The teams identified two drivers that had direct ties to the reduction of load during Winter Storm Elliott:
- Rain followed by extreme cold weather and wind created an environment that was beyond design basis of TVA generating sites, causing some units to trip offline causing a generation deficiency;
- Due to the regional nature of the weather event, energy market purchases were curtailed, contributing to the generation deficiency.
In addition to direct drivers of the event, the teams identified improvement opportunities in each category and what TVA did well in each category.
TVA said it recognizes the importance of reviewing the actions taken during Winter Storm Elliott to identify improvement opportunities and address those areas.
Several opportunities were identified across the categories:
- The importance of accurate forecasting to utilities can’t be overstated, and in this instance, TVA’s operational and real-time industry load forecasting tools did not accurately predict the load or the potential risks experienced during Winter Storm Elliott.
- While no gas generation units tripped offline because of gas pressure issues from the interstate pipelines, the gas fleet identified opportunities for improved communication across the fleet and TVA, to enhance coordination and visibility related to gas supply, pressure alignment and troubleshooting.
- The flow of information, both internally across the organization and externally with customers, stakeholders, and the public, was not timely or fully effective, which resulted in inconsistent messaging and lack of situational awareness and expectations, and slow internal coordinations, approvals and stakeholder responses.
- Slow internal coordination and approvals resulted in delayed information-sharing, social media updates, and responses to customers.
- There are opportunities for better coordination and implementation of emergency procedures and protocols across the agency.
While TVA found itself for the first time in its history directing local power companies to reduce their load, with many executing rolling outages to meet the request, several areas within TVA did perform well and should be considered strengths, the report said.
For example, employees at sites stayed focused on safety, even during very challenging weather conditions, and successfully performed their duties without incident throughout the storm.
Also, the execution of the Emergency Load Curtailment Program worked well. TVA’s Transmission and Operations center executed the program as designed and local power companies responded quickly when called upon, supporting grid stability and reliability.
In addition, interruptible products, providing the needed load reductions, outperformed expectations, the report said.
Also, a reserve sharing agreement with Louisville Gas & Electric/Kentucky Utilities, in which LGE/KU and TVA make energy available to each other when outside assistance is needed, worked as designed.
And TVA’s regional external relations model “enabled strong local engagement and outreach with customers, public officials and communities to help resolve challenges.”
In addition, TVA’s transmission system performed well throughout the storm.
Near and Medium-Term Actions Identified
Based on TVA’s review the team identified a number of near- and medium-term actions to address the drivers and improvement opportunities. “While TVA teams have already started addressing some of the actions, others are being planned to ensure completion in the coming months,” the report noted.
The report also details TVA’s plan to help meet the region’s growing capacity. Among other things, between 2023 and 2027, TVA will invest $12 billion for capacity expansion and base capital and it is building about 3,800 MW of new generation, including combustion turbines, solar projects, combined-cycle natural gas, and energy storage.