When she awoke Sunday morning to an apartment with no power, Linda Zukowski thought, “Here we go again.”
Thinking back to the two-day Back Bay blackout of March 2012, Zukowski said she was preparing for the worst.
“I didn’t have much food, there was no coffee, I had forgotten to charge my phone,” she said.
Luckily, reality was not as bad as Zukowski initially feared and she had power restored before noon.
At about 3:15 a.m. Sunday, a cable that connects a transformer to the electrical grid at the Scotia Street substation — the same facility that was at the center of the March 2012 outage — malfunctioned and cut power to about 12,000 customers between the Charles River and Columbus Avenue, and between Copley Square and the Fenway neighborhood, said NStar spokesman Michael Durand.
Since the March 2012 outage, NStar has been working to upgrade the Scotia Street facility. Durand said it is “about a week away from being a brand-new substation.”
In order to get the system back to normal operations, Durand said, NStar planned to shut down power for a few hours early Monday morning to the customers affected, while crews fixed the underlying problem at the substation.
Officials said the Massachusetts Turnpike’s Prudential tunnel would be closed to traffic during the work, starting at about 1 a.m.
The repairs were expected to be completed by 5 a.m. Monday, Durand said.
“Now everything we need to do is taking place behind the scenes or overnight as we bring the system back to normal,” he said.
Durand said around 8,000 of the affected customers had power back by about 9 a.m. Sunday and that after 10 a.m. only a handful of customers remained without electricity. By noon, power was restored to all customers.
In March 2012, a break in the connection between a power line and a transformer at the Scotia Street substation caused a cooling agent inside the line to spew onto an electrified area, igniting a smoky fire and causing a two-day blackout in one of the city’s busiest residential and commercial neighborhoods.
On Sunday, one of the two transformers at the substation was out of service for upgrades and if both had been in place, “it would have been a nonevent,” NStar president Craig Hallstrom said.
Part of the upgrade work during the past year, Durand said, involved putting contingency plans in place. Those plans helped minimize the duration of Sunday’s power outage, he said.
Though many restaurants had power back by around 9 a.m., one ice cream shop manager said she initially feared the worst for her product.
“I had a mini-heart attack and thought we’d have to get dry ice for the freezers,” said Devin Handley, manager of the Newbury Street Ben & Jerry’s. “We just kept our fridges closed and luckily things were back to normal around 9:30 a.m. The ice cream is just fine.”
For residents, the early morning outage was an inconvenience that threw normal routines to the wayside.
“It’s been a real pain in the neck,” said Annabeth tenBroeck, who lives on Huntington Avenue. “Everyone in the building was just trying to find a good cup of coffee. . . . I had to take a candlelit shower. It’s been a miserable morning.”
The power outage closed the Massachusetts Turnpike around the Prudential tunnel in both directions and created backups in the area. Traffic was back to normal by afternoon, according to State Police.
About 30 more NStar customers across six or seven buildings near the intersection of Beacon Street and Massachusetts Avenue lost power Sunday night after flames burst from a manhole at about 8:45 p.m., officials said.
Bill Zamparelli, a spokesman for NStar, said the underground fire was not connected to the earlier outage, even though the fire started in the same network of circuits.
After power was restored in the 2012 Back Bay outage, a sudden surge in demand for power caused underground cables to fail and sent manhole covers soaring into the air.
Zamparelli said the cause of Sunday’s fire was unknown.
Trish Fuller said she was standing outside her apartment building on Beacon Street about 10 feet from the manhole. She saw smoke pouring from the manhole and then lights inside buildings up and down the block began violently flickering.
She yelled out to a man who was about to walk right over the manhole.
“I said: ‘Stop, that’s going to blow up,’ ” Fuller said.
The man stopped. Flames shot several feet in the air once, and then again.
Afterward, she said both she and the man were shaking and the man, who she had never met before, gave her a hug.
“It was terrifying,” she said. “Especially after those Marathon bombings.”Globe correspondents Evan Allen and Matt Rocheleau contributed to this report. Colin A. Young can be reached at email@example.com. Follow him on Twitter @ColinAYoung. Alyssa A. Botelho can be reached at firstname.lastname@example.org. Follow her on Twitter @AlyssaABotelho.