Duke Energy errors, equipment failures found during rolling outages, report says

Duke Energy errors, equipment failures found during rolling outages, report says
Published: Sep. 1, 2023 at 12:31 PM EDT|Updated: Sep. 1, 2023 at 1:48 PM EDT
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COLUMBIA, S.C. (FOX Carolina) - A new report from the Office of Regulatory Staff (ORS) is revealing what led up to rolling power outages for Duke Energy customers during a winter storm across the Carolinas on Christmas Eve. The report alleges Duke Energy had an inadequate power supply, experienced multiple equipment failures, delayed notifying customers until after the outages began, and experienced a software failure that resulted in delayed restoration.

Approximately 500,000 customers across South and North Carolina were affected by the rolling outages, with 94,893 of those customers in South Carolina. On average, customers were without power for just under three hours. However, some customers were in the dark for over ten hours.

In January, the Public Service Commission requested the ORS investigate the rolling outages to determine their cause and how they could be avoided during future weather events.

The report identified five key causes for the rolling outages: Duke Energy “significantly” underestimated demand and experienced multiple failures at various plants, power purchases from neighboring utility companies were curtailed, power generation contracted by other utilities failed, and a software tool to manage the rotating outages failed.

The report found Duke Energy made an estimation of power demand for December 24th, the day of the rolling outages, on December 23rd, and failed to update its estimations as the day went on: “Duke Energy’s large load forecasting error contributed to its failure to anticipate the significance of the holiday weekend and led to shortfalls in its supply planning…”

The investigation also found multiple plants were unavailable because of planned maintenance, while other plants failed because of operational issues that forced them to shut down. In one case, the investigation found that a plant was damaged because a door was left open, exposing the machinery to cold air. Other issues cited included cracks in insulation and frozen instrumentation.

Duke Energy purchased power from neighboring utilities, however, the power actually available was curtailed, or reduced, on the day of the freeze because of widespread stress on those neighboring systems.

Duke Energy also dealt with failures in its automated software, RLS, beginning at 6:57 a.m. on Christmas Eve, approximately 30 minutes after the rolling outages began. The RLS tool is designed to rotate customer outages on a 15-30 minute basis. The report details that, because of this software failure, Duke Energy had to manually restore power, which significantly delayed the restoration by several hours in some cases.

The report also found issues with how Duke Energy communicated its intention to initiate rolling outages to customers. The outages began between 6:15 and 6:25 AM on December 24th. The report found Duke Energy began notifying customers one hour later. The investigation also found Duke Energy told customers the timeframe for power restoration would be 30 to 60 minutes, when in reality it was several hours.

Ultimately, the report found there is “room for improvement” in Duke Energy’s Cold Weather Preparedness Plans at its generation facilities. The investigation made several recommendations, including ensuring that doors and louvers that could expose equipment to the elements are left closed, and installing heaters. The investigation also recommended Duke enhance staffing and the frequency of operators making rounds during severe winter weather events.

Duke Energy submitted a letter to the Public Service Commission responding to the report, which took issue with several of its findings. Duke Energy said the models it uses to forecast power demand “look backwards in time” for similar circumstances, and that a similar day in December did not exist.

Duke Energy also said it “cannot commit” to notifying customers before rolling outages begin, but that it would implement a notification process.

The ORS presented its report to the Public Service Commission on September 1st. During the presentation, ORS representatives acknowledged Winter Storm Elliott brought unique challenges experienced by many utility companies, not just Duke Energy.

Duke Energy did enter into a corrective action plan, however, the tracking of their progress is marked as confidential and was not immediately available. In its letter to the Public Service Commission, Duke Energy said it completed 76 of the 101 action items in the correction plan.

A spokesperson for Duke Energy released the following statement regarding the report: