August 21, 2020

How Duke Energy is strengthening the grid for floods

Many things can delay power restoration after a major storm, from damage caused by fallen trees to outages in remote, hard-to-access areas. But, one of the most difficult challenges, especially in recent years, is flooding. Floods can wash away roads – like they did after 2018’s Hurricane Florence – and submerge entire towns making it impossible to repair the grid until water recedes.

To help avoid these delays, Duke Energy is strengthening the grid against floods. The company is installing reinforced flood barriers and relocating equipment at 13 substations in flood-prone areas of eastern North and South Carolina.

Substations are a critical part of the grid – they take the electricity carried by high-voltage lines from a power plant and convert it to a lower voltage compatible with smaller power lines in communities. If a substation is down, it can mean power outages for thousands of people. Since Hurricane Matthew in 2016, the Carolinas have experienced two 500-year floods, a 1,000-year flood and some of the strongest hurricanes in decades. 

Researchers at NOAA determined that from 1958 to 2016, heavy rains have increased by 42 percent in midwestern states and 27 percent in the southeast. With an extremely active hurricane season already underway in 2020, the company wants to be prepared.

Duke Energy analyzed previous storms and developed custom flood protection measures for 13 historically affected sites. They are constructing barriers around equipment or the entire site, raising equipment or relocating it to less flood-prone areas.

Seven substations will have reinforced walls made of a non-conductive fiberglass material or PVC (finishes like you’d feel on a boat hull), with aluminum access gates. The gates are installed when the company forecasts potential flooding. When flooding is not anticipated, the gates are open so crews can quickly access the substation for maintenance. Mike Sykes, who manages the project, said these materials are durable and cost effective compared to other options like steel or concrete. The walls are 6- to 8-feet high depending on expected flood levels and land survey data. They're anchored 12 to 25 feet underground to withstand strong winds.

Here’s drone footage of protective flood barriers installed at a substation in Wallace, N.C., about 40 minutes northwest of Wilmington, which saw substantial flooding when Hurricane Florence poured 9 trillion gallons of water on the state in 2018.

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