Why Restoring Power After Helene Is Complicated

Damage went beyond downed power lines. Hundreds of substations went out after the storm. Getting them back online is difficult.

Hurricane Helene didn’t just knock down power lines across the Southeast — it also flooded many electrical substations, which can take weeks or months to repair if they are severely damaged.

Substations are critical pieces of infrastructure that connect high-voltage transmission lines with smaller distribution lines that feed power to communities. As crews race to restore electricity to hundreds of thousands of homes across North and South Carolina, their task is complicated by the extensive destruction caused by the storm and the inaccessibility of some of the hardest-hit regions.

Duke Energy, the largest electric utility in the Carolinas, said that about 370 substations in its territory were knocked out of service by Helene. The “vast majority” of those outages were caused by damaged power lines and many of those substations have already been restored, said Jennifer Garber, a Duke spokeswoman.

But an unknown number of substations may have faced more extensive damage from the floods. If they cannot be repaired quickly, Duke is aiming to bring in mobile substations to restore service as soon as it is safe to do so, though that could prove difficult as many roads remain destroyed or blocked by debris.

“The devastation of Hurricane Helene is unlike anything we have seen before in the Carolinas,” Ms. Garber said.

As of Tuesday morning, about 346,000 homes and businesses in North Carolina and 446,000 customers in South Carolina were without power. In a statement, Duke said that it aimed to restore electricity to most customers by Friday night, though it cautioned that the process “may take longer in areas that continue to be inaccessible, dependent on infrastructure that has been destroyed or are unable to receive service.”

In the Upstate region of South Carolina, the damage was particularly extensive and “we believe that 50 percent of the outages will require significant replacement of infrastructure,” Ms. Garber said.

The time it takes to repair a substation can depend on what equipment is affected. The most important component is the transformer, which steps up and down the voltage of electricity. There is currently a global shortage of transformers because of soaring demand from renewable energy developers, according to Wood Mackenzie, a consulting firm. Wait times for some new equipment can be two to three years, on average.

Scott Aaronson, senior vice president of security and preparedness at the Edison Electric Institute, a trade group, said he did not expect the transformer shortage to be a major problem for Helene recovery efforts. He said many power companies have plans to stockpile or share replacement equipment, and the largest bulk transformers on the grid — which often are the hardest to replace — mostly appear to have survived the storm.

The bigger problem is reaching the damaged infrastructure, he said. “What’s been unique about this storm has been the inability to access certain parts of the region,” Mr. Aaronson said. While utilities can use helicopters, drones and satellites to survey damage, those methods have limitations.

Duke Energy said it had already restored power to 1.35 million customers since Sunday, mainly to people living outside of the mountain region of North Carolina and Upstate South Carolina.

In some cases, the destruction has been so severe that homes and businesses can no longer receive electricity. “In that case, we’re not talking about restoring power — we’re talking about completely rebuilding,” Mr. Aaronson said.

Utilities can sometimes reroute power or set up mobile substations on trucks as a temporary fix. Hurricane Florence, which battered the Carolinas in 2018, knocked out seven of Duke’s substations as well as a number of substations owned by smaller electric providers. The majority of customers saw power restored within days, though several thousand people across the region still did not have service three weeks later.