How Chattanooga’s self-healing smart grid is cutting outages, saving money


The US city of Chattanooga in Tennessee has built the most automated electricity system in America and has seen a big drop in the length and scope of power outages.

Chattanooga’s smart grid was put to the test in February 2014 with a major snowstorm.

The grid prevented power outages or automatically restored electric power to about 40,000 customers, representing more than a 50 per cent reduction in the number of customers who otherwise would have experienced a sustained outage.

Forward-thinking utility

Engerati had the opportunity to speak to S&C Electric’s vice president of Strategic Solutions, Tim Qualheim about EPB’s recent grid development. He was quick to point out how “forward-thinking” the utility is as they put their customers’ comfort and needs first. He says, “They don’t view their customers as mere ratepayers. They are sincerely concerned about their customer’s needs and want to improve electric reliability to help improve their residents’ lives.”

He added that the utility also realised that they had to build a future-ready grid. “Knowing they would need to replace their electric system over the next 30 years, rather than replacing poles and equipment like for like, they chose to improve the system. The aim is to grow the community by improving power access and reliability.”

The main plan was to reduce costs for both the utility and its customers, as well as improve system reliability especially during major storms which can lead to lengthy outages.

The city’s local utility EPB installed roughly 1,200 S&C IntelliRupter PulseClosers with IntelliTeam SG Automatic Restoration System to provide rapid response to power system disturbances. In the event of a power outage, the IntelliRupters communicate with each other over EPB’s fiber optic network to identify where the fault occurred, and then quickly reroute power to restore service to as many customers as possible.

“The S&C Electric’s system was chosen for reliability improvements, partly because it is future proof,” explains Mr Qualheim, “It has capabilities to enhance system operation well beyond even today’s advanced performance.”

Exceeds reliability target

The system has automated several manual processes and eliminated much of the chaos that typically accompanied an outage. The system is able to locate a fault, isolate it, and restores unfaulted customers automatically in less than a minute,” explains Mr Qualheim. “Fewer people see an outage from the fault, saving those folks the aggravation and cost of an outage.  The dispatcher immediately knows exactly where the fault is, allowing restoration crews to reach it faster and restore service more quickly, which not only reduces the outage time and costs to the affected customers, it also saves EPB restoration costs.”

The system has helped the utility to exceed their reliability improvement target of 40%-in the past year, they have managed to reduce outages by over 60%.

The advanced system has also allowed the utility to adopt new system protection schemes and operating practises in response to the new efficiencies.

Shortly after the system was implemented, the city was hit by a major storm. The July 2012 storm was one of the century’s biggest. Despite this, the utility was able to keep half of its customers connected to the grid. Restoration times were quicker too-before the new system, restoration would take five days. With the new system, the utility was able to restore customers in less than three days-a major improvement.  In addition to the customer benefits of faster restoration, the utility managed to save US$1.4 million dollars in lower restoration costs.

Three components to consider

Mr Qualheim says that utilities implementing automation should focus on these three components:

1.     A robust communications system. Chattanooga had the foresight to see that it needs a more impressive communications system and there are multiple ways in which to do this. Mr Qualheim suggests that utilities have their own licensed frequency or their own fibre optics communications system (like Chatanooga). “This will ensure that you are prioritized during an emergency.” With this in place, utilities can even establish auxillary services.

2.     Utilities need future proof equipment like IntelliRupters that will facilitate 21st century operations. Robust, intelligent field devices are a necessity.

3.     Utilities should opt for layered intelligence, with a central control system implementing system level policy, and with distributed intelligence performing the feeder level functions more quickly and effectively than central systems can.  This combination provides for a much more resilient, reliable and scalable future grid.

Chattanooga’s smart grid is delivering major benefits today by reducing the cost of power outages. The city’s reliable power is also attracting new business, thereby increasing economic development. Existing businesses can also operate in the knowledge that outages are more controlled and that access is re-established quickly during outages.

The city’s smart grid results show how automation solutions can deliver immediate, tangible results to the community, while also laying the groundwork to support future grid uses.

Engerati is the sister portal to, focusing on smart energy.