Island-wide power outage triggered during summer maintenance, says N.L. Hydro

A power outage that left tens of thousands of Newfoundland Power customers without power Sunday was due to a malfunction that popped up during routine summer maintenance, says one of Newfoundland and Labrador Hydro's vice-presidents.

N.L. Hydro engineering vice-president Rob Collett said crews were doing maintenance work on a piece of equipment in one of the utility's terminal stations in Labrador.

"It actually didn't originate in the plant at Muskrat Falls. It didn't originate with the Labrador-Island link," Collett said Monday morning.

"It actually started in our switchyard and with a device called the circuit breaker."

Customers across Newfoundland lost power for half an hour before it was restored.

Collett likened the situation to a home where there are circuit breakers that correspond to specific functions like the hot water boiler — if people want to, say, change out a thermostat, he said, the corresponding breaker needs to be switched off first.

"We were doing a similar thing yesterday. We were working on a circuit breaker in our switchyard."

During that work, "something unexpected happened," Collett said, and the system reacted.

"And as a protection to the system, that kind of triggered a bigger response and then everything got disconnected."

He said it happened at the Muskrat Falls terminal station, where the Muskrat Falls generators tie into the system and the Labrador-Island link.

"When you disconnect them from each other, there's no power to flow over the Labrador-Island link. And when that happens, there's a shortfall of supply on the island," said Collett.

"So when the supply and the demand aren't equal, we have to cut the customers off using, again, these circuit breakers."

Investigation ongoing

Sunday's massive power outage was a rare and isolated incident, he said. There are typically measures in place that would isolate a system so a bigger problem, like an outage, doesn't spread. It's not clear what triggered the issue, he said, but they do know it wasn't an equipment issue.

He said the maintenance being done was routine summer work to prepare for winter, when there's more demand for power.

"What happens is, typically, is that we're able to isolate all the systems around the circuit breaker. It then sits in isolation with no ability to impact the larger system. What happened yesterday was totally unexpected."

He said the issue knocked out the whole Labrador-Island link, which carries more than half the power supply to the island.

There will be a statement after the investigation concludes, he said, noting that all power outages have to be reported to the provincial Public Utilities Board.

"We're doing an investigation on this now and just to ensure that this does not happen again," said Collett.

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