Disaster Response and Mutual Aid

Chattanooga’s smart grid prevented around 44,000 customers from losing power

Chattanooga, Tenn.’s smart grid prevented about 44,000 customers from experiencing a power outage that would have lasted hours or perhaps days when tornados, heavy storms and high winds rolled across the community earlier this month, EPB, the city’s public power utility, recently reported.

EPB has deployed a comprehensive community-wide fiber optic network accessible to every home and business in the utility’s 600 square mile service area, noted J.Ed. Marston, Vice President for Marketing at EPB.

“In addition to utilizing the network to deliver the world’s fastest internet and other fiber optic services, Chattanooga’s fiber to the home network also serves as the communications backbone for a smart grid that includes 1,200 automated smart switches, more than 180,000 smart meters on all electric facilities, and other smart grid equipment,” Marston said in an email.

Taken together, Chattanooga’s smart grid has been programmed to continuously monitor for damage to the electric system and to automatically re-route power around any faults to minimize the outage. As a result, Chattanooga’s smart grid is able to respond nearly instantaneously to auto-restore many customers who might otherwise have to wait hours for a manual switching process to take place.

Jim Glass, Manager of Smart Grid Development at EPB, noted that the avoided customer outages were based upon two conditions.

The first condition involved customers who were automatically restored by the distribution automation – usually in a few seconds.

The second condition reflected customers who were “upstream” of the automated switch that locked out. “Prior to our distribution automation equipment deployment, these customers would have experienced an interruption due to the feeder breaker locking out,” Glass noted. “Today, an automated switch closer to the fault opens and the customers between this switch and the breaker remain in service,” Glass said.

EPB estimates damage from tornados and storms at more than $28 mil

In the wake of the tornados and severe storms that ripped through the Chattanooga area on April 12, EPB on April 24 said it estimated more than $28 million in damage to the community’s electric and fiber optic infrastructure. This exceeds the $25 million damage total from the tornados that impacted the area in 2011.

“The devastation from this storm focused on some of the most densely populated parts of our community and consequently heavy concentrations of infrastructure were destroyed,” said David Wade, president and CEO of EPB. “Our first thought was for the families impacted by the storm, and we knew the most important thing we could do was to re-build the system so we could restore power and connectivity to as many as possible as quickly as we possibly could.”

 With the benefit of post-restoration information and analysis, Wade was able to share a more detailed and complete outline of storm preparation, damage, and restoration efforts.

With severe storms in the forecast, EPB had called in additional crews beforehand. As tornados, heavy storms, and high winds rolled across the community after 11 p.m. on Easter Sunday, more than 106,000 EPB customers lost power. Almost instantaneously, Chattanooga’s smart grid began its automated processes which prevented about 44,000 customers from experiencing an outage that would have lasted hours or perhaps days.

EPB noted that this allowed the utility to immediately focus on repair efforts for about 62,000 customers who remained without power. Line crews immediately went to work. Within 24 hours, EPB had restored power to 20,000 more households while beginning the process of calling on mutual aid agreements with other utilities.

Through that effort, EPB was able to accelerate the effort of re-building a substantial portion of Chattanooga’s electric and fiber optic system by temporarily growing its workforce by more than 1,500 utility workers from across eight states.

 As EPB continued the re-construction, the full picture of the devastation became clearer and clearer. Crews had to remove many tons of trees, debris, and damaged equipment before they could even begin to rebuild the shattered infrastructure. A preliminary survey of the damage and re-construction includes:

  • Three substations that distribute power to a wide swath of Hamilton County had been knocked off-line requiring a major clearing and re-building operation before they could be re-energized.
  • 812 utility poles had fallen, broken or shattered during the storm, requiring removal and replacement.
  • 709 transformers were destroyed requiring removal and replacement.
  • 125 miles of power line had to be replaced and re-strung over a 65-mile span of infrastructure.
  • About 500 homes were too damaged for safe power restoration requiring the removal of electric facilities to the premises until repairs or re-construction can take place.

 EPB established major staging area and support station

To keep utility workers wholly focused on these re-construction efforts as they worked sixteen-hour shifts, EPB established a major staging area and support station in the parking lot of a mall.

Utility workers could come to these locations to get the materials they needed along with a quick meal, so they could return to the job.

EPB employees who typically work in office positions continued to be responsible for their normal work while also volunteering to put out food, distribute protective gear, and coordinate the staging of re-construction materials.

“When you count all of the utility crews we brought in along with all of EPB’s regular employees who joined in restoration efforts, we were able to dedicate more than 2,000 people to the sole focus of restoring services to our customers,” Wade said. “At a time when so many in our community are facing severe challenges, everyone at EPB shared a sense of purpose in helping our neighbors take the first steps toward re-construction.