Wilson Dam Legacy Lives On

TVA’s Largest Hydro Facility Gets New Lease on Life

In northwest Alabama, Wilson Dam stretches across the Tennessee River with 21 operating units that have an output of 653 megawatts – powering more than 380,000 homes.

The largest conventional hydroelectric facility in the TVA system, Wilson is unique with its neoclassical-style architectural design and the highest single-lift lock east of the Rockies, through which more than 3,700 vessels pass each year.

The Ultimate Juggling Act

Wilson Dam is undergoing four simultaneous upgrades.

With 21 units that each need to be taken offline every three years for maintenance, it isn’t uncommon to juggle multiple upgrades at once. Unlike other technologies in TVA’s fleet, hydro outages may flex outside of the typical spring or fall timeframes.

For example, summer is usually when TVA has peak demands and wants all available assets running.

Sometimes summer means drought, however, and that means there isn’t enough water available to run a hydro facility at full capacity, making it a prime opportunity to take units offline and undergo maintenance. In contrast, when the South is drenched with rain in the winter months, the increased water flow is perfect for full operation.

Maintenance and Upgrades

Unit 18 is in the middle of a 40-day outage for routine inspections. These inspections evaluate various components and systems, with any related repairs scheduled soon thereafter.

Units 5 and 6 are undergoing maintenance to upgrade the generator leads and install new relays – which take the electricity created by the generator and send it out through the transmission lines to power the region.

“The generator leads on Units 5 and 6 are the last two of the original eight units that completed the upgrade from essentially an insulated cable to an upgraded bus, or metal strips that conduct electricity,” said Jimmy Springer, hydro support supervisor. “The generator leads were original equipment to the plant – so from the early 1920s – and the upgrade will allow the opportunity to increase megawatt output of the units with future equipment upgrades as part of what we call hydro life extension outages.”

In addition to the upgrades, Unit 5’s exciter – the equipment that controls the output voltage of the generator – was also removed, refurbished by the Power Service Shop, and reinstalled. During refurbishment, the Power Service Shop team checked the windings, machined the slip rings and reinsulated to address known issues.

Unit 3 is currently experiencing rotor issues. Slated for a hydro-life extension in 2027, reviews are ongoing to determine the best options to extend the life of the unit.

Specifically, TVA teams are looking at conducting a phase neutral swap on any generators older than 25 years. If the generators are upgraded, it could add 4-5 megawatts per unit and extend their lifespans. 

Generating Today, Tomorrow and Beyond

It takes quite the team to keep all these units running.

TVA is looking to hire 20 new technicians to undergo a training program to prepare the next generation workforce to keep this historical and critical asset operating for years to come.

Investing in the next generation is an important part of what plant manager Tabby Lolley does for the region.

“We had more than 200 local students come through and tour the plant recently,” she said. “I remember when I toured the plant when I was in sixth grade, and now I get to do that for the next generation – it’s really special to be part of the Wilson Dam legacy.”