Equipment failure, among other reasons, to blame for Duke Energy outages on Christmas Eve

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For the first time in company history, Duke Energy declared power outages on Christmas Eve in freezing temperatures. This decision left half a million customers without power. And on Tuesday, the company issued an apology, attributing several aggravating factors to its reasoning.

“I want to express how sorry we are for what our customers went through. We own what happened,” said Julie Janson, executive vice president and CEO of Duke Energy Carolinas. “Make turning stops [was] necessary to protect network integrity and mitigate the risk of severe failure affecting many more customers for longer periods of time. »

The North Carolina Utilities Commission asked Duke Energy about the situation during a public briefing on Tuesday.

Equipment failure due to severe cold and inaccurate modeling contributed to the outages. Duke said there was extremely high demand and not enough electricity.

Three of Duke’s power plants, Dan River, Mayo and Roxboro, had to cut operations in half because instrumentation lines froze, causing Duke to lose 1,300 megawatts of electricity. This happened despite these lines having weatherization measures.

“This equipment had functional insulation and thermal freeze in operation, and yet time was able to overcome these circuits,” said Preston Gillespie, the company’s production manager. “We have some assessment work to do to understand why this happened on these particular pieces of instrumentation and did not happen on others.”

Duke attempted to increase its supply by purchasing electricity from nearby utility providers, such as PJM Interconnection. However, PJM and other companies had similar problems with the cold, so the power never came.

Finally, Duke relied on a modeling system used to predict customer demand.

On the evening of December 23, this model predicted having enough power generation reserves to meet peak demand the next morning.

This estimate turned out to be wrong. This model operates on the basis of past events and, as Nelson Peeler, Duke’s transmission manager pointed out, this was an unprecedented weather event.

“It was a very cold day in December…with very high winds. The holidays make it more complicated,” Peeler said. “The model tries to determine how the load will behave. So, for example, what industrial or commercial loads are there on a Saturday [on] Christmas Eve? It’s a challenge to predict without a story.”

Officials said the weather over the holiday weekend brought the coldest December temperatures to North Carolina since the 1980s.

Once the model had data from Christmas Eve, it was able to accurately predict demand for Christmas Day and beyond.

Yet another system went down after operators started rolling outages. This system is supposed to automatically cut power to customers and then automatically bring them back online. However, this system failed around 7am on Christmas Eve. We still don’t know why.

This required operators to manually cut power and manually restore it. Operators worked to restore power until around 4 p.m. on Christmas Eve.

This system failure resulted in much longer outages than expected.

“We deeply regret that some of our customers were without power for an extended period on Christmas Eve, but given the difficult situations our operators faced, they have taken appropriate action,” said Scott Batson, Director of Distribution at Duke Energy.

Duke told the Utilities Commission it was investigating why its automatic system failed and why its weatherproof gear froze.

Duke also intends to evaluate how it communicates with its customers. The company has been criticized for not informing customers of outages in advance.

State Utilities Commissioner Floyd McKissick said Duke’s customer notification system should be upgraded as soon as possible so people can be prepared.

Additionally, the Federal Energy Regulatory Commission has launched an investigation into the power outages. Duke said he would fully commit to and comply with this investigation.

It comes shortly after two electrical substations operated by Duke Energy in Moore County were shot down and damaged by gunfire, causing widespread outages for several days. There is currently no evidence that these two events are related.

The Associated Press contributed to this report.

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