N.C. Outer Banks Blackout Tests Co-ops

North Carolina electric cooperatives that serve Outer Banks communities are working to restore permanent power to their members following a construction mishap and say they are learning more about their microgrid in the process.

After mounting new poles, crews from CHEC connect new overhead lines to the underground cable and to existing overhead lines on Hatteras Island. (Photo By: CHEC)

After mounting new poles, crews from CHEC connect new overhead lines to the underground cable and to existing overhead lines on Hatteras Island. (Photo By: CHEC)

Cape Hatteras Island and Ocracoke Island lost air conditioning and refrigeration at the height of beach season July 27 when a bridge construction team mistakenly drove a steel casing through underground transmission cables.

"Crews continue to work around the clock to get Hatteras Island back open to the public as soon as possible," said Laura Ertle, director of public relations and marketing at Cape Hatteras Electric Cooperative (CHEC) in Buxton.

All repairs are expected to be completed within three to five days, CHEC said Aug. 2.

Two of three underground transmission cables owned and operated by CHEC were damaged July 27 during construction of a new bridge, the co-op said. The blackout of Hatteras and Ocracoke islands occurred at 4:30 a.m. and took out about 10,000 meters.

On July 31, CHEC began building overhead transmission as one of two simultaneous solutions to full power restoration. The new line will run from the southern tip of Bonner Bridge, which connects the northern Outer Banks with Hatteras Island, to the co-op's existing overhead line.

CHEC's transmission carries electricity from the mainland south across Oregon Inlet to Hatteras Island. It then runs for 50 miles before crossing another inlet to Ocracoke Island. Tideland EMC, headquartered in Pantego, serves Ocracoke.

CHEC was also working to repair the damaged underground cables. The co-op had dug out and spliced one severed cable July 30 and had excavated the others in the days following, but on Aug. 2 CHEC said it determined that trench conditions to complete repairs “proved to be too challenging” as water continued to seep in.

“The overhead transmission line construction has emerged as the fastest, safest way to restore transmission service to Hatteras and Ocracoke Islands,” said Kristie Aldridge, digital communications manager for North Carolina Electric Membership Corporation.

At present, residents that remain on Hatteras Island have continuous temporary power through emergency generators.

North Carolina Gov. Roy Cooper pledged state resources to aid the restoration and manage the emergency when he visited the construction site July 31.

"I appreciate the hard work utility crews are doing to get the power back on and we must help them get the work done quickly," Cooper said. "State resources are available to help Hatteras and Ocracoke and we'll do all we can to get repairs moving."

CHEC’s underground transmission cable was cut July 27 during construction of a new bridge to Hatteras Island on North Carolina’s Outer Banks. (Photo By: CHEC)

CHEC’s underground transmission cable was cut July 27 during construction of a new bridge to Hatteras Island on North Carolina’s Outer Banks. (Photo By: CHEC)

Officials ordered thousands of tourists enjoying the peak vacation season on Hatteras and Ocracoke to evacuate during energy emergency. CHEC  and Tideland continue to urge permanent residents who remain on the islands to conserve electricity usage.

Tideland located and coordinated delivery of three mobile generators by ferry after the existing 3-megawatt diesel generator on the island broke shortly after the blackout.

A 1-MW mobile generator arrived the night of July 27 and co-op crews energized it by 3:30 a.m. July 28. Two 2-MW generators got to the island that afternoon. 

By midday July 29, both co-ops had restored their members, the full-time residents, with generator power.

Consumer-owned generators on Ocracoke, as well as microgrid components, also helped restore electricity to the island's 1,313 meters and ward off further maintenance outages, Tideland officials said.

"We learned a lot about microgrid components," said Heidi Jernigan Smith, manager of economic development, marketing and corporate communications at Tideland. "The best classroom sometimes is real life."

The microgrid's Tesla battery bank cycled multiple times at 500 kilowatts each time to support the grid, North Carolina Electric Membership Corporation, the co-op's G&T, said. Solar panels on the roof of the Ocracoke diesel generator also added power to the grid.

The microgrid's residential component of Ecobee thermostats and water heater devices also helped reduce load. At present about 183 island members can control residential air conditioning demand with the thermostats, even remotely. 

Developed and interconnected by NCEMC and Tideland, the microgrid first energized in February.

"We look forward to utilizing data gleaned from these past few days to improve our microgrid performance," said Lee Ragsdale, NCEMC's senior vice president of grid infrastructure and compliance.

This story was updated August 2 to reflect a change in the projected repair time.


ADVERTISEMENTS
MORE FROM NRECA