How hydro workers got our power back on in 52 hours

One of Ottawa's two major power sources was decimated by one of three tornadoes to hit the region on Friday, leaving 180,000 homes without power. Yet by late Sunday night, it was less that 4,000. How did it happen?

'I've worked at Hydro One for 30 years, and I've never seen anything like that'

The Hydro One-owned Merivale transformer station was badly damaged by high winds, disconnecting parts of the city from the provincial transmission grid. (Supplied by Hydro One)

After three tornadoes ripped through the Ottawa region Friday, leaving 180,000 homes in the city without power, Hydro Ottawa boss Bryce Conrad had a grim phone conversation with his provincial counterpart.

"Our call was fairly devastating," said Darlene Bradley, acting chief operating officer for Hydro One.

The Merivale transformer station sits near the Greenbank and Hunt Club area, where one of the tornadoes touched down. Roofs were ripped off buildings, the porcelain insulation that protects power cables was smashed, and debris was everywhere. Not a single piece of equipment was working.

"I've worked at Hydro One for 30 years, and I've never seen anything like that," Bradley said. "There was nothing that was usable."

And yet, a little more than 48 hours later, the number of homes without power was down to just fewer than 4,000.

How did they do it?

Residents are combing through the wreckage of their homes and reaching out to help neighbours after tornadoes ripped through Ottawa-Gatineau on Sept. 21. 2:47

Rejigging the system

In addition to the damage at the Merivale station, 90 hydro poles had fallen, pulling wires down with them. Transmission towers were folded in half.

So late Friday, Hydro Ottawa crews — mostly workers who had finished their shift Friday afternoon and stayed on when the weather warning arrived — began working on the poles and clearing debris. Crews laboured tirelessly around the clock.

Getting those wires up would give some people their power back, or at the very least, get the network ready for the flow of power.

In the meantime, Hydro One investigated how to divert power from the Hawthorne transformer station to the dark areas of the city.

Hydro One transmission towers near the Merivale transformer station were folded in half by the winds. (Hydro One)

"It's like running an extension cord to your neighbour's house so you can have power while you fix your own house," Bradley said.

Normally the city's electricity network works at 60 or 70 per cent capacity, leaving room to add load to other parts of the system. That strategy worked — to an extent.

By Saturday morning, the combination of rerouting power and repairing poles had restored electricity to 30,000 customers. Hydro workers continued to have success through the day and night on Saturday. By Sunday morning, power had been restored to a total of more than 100,000 homes.

Why does my neighbour have light?

But the workaround wasn't perfect.

Rerouting didn't always allow Hydro Ottawa to bring power to whole communities. In some cases, just a few small neighbourhood distribution systems, or circuits, received power. That meant some residents were burning candles while their neighbours across the street had the lights on.

It was confusing and frustrating for many.

Worse, hydro officials always knew the rerouting wouldn't bring power to every home. At some point, they needed to flow power through that Merivale station, which seemed impossible at the start of the weekend.

Like a puzzle

But Hydro One engineers and technicians had been thinking about the problem as their crews handled the dangerous work of cleaning the station.

Merivale acts as a sort of bridge between the provincial and municipal hydro networks. High-voltage power comes into the Hydro One station, gets transformed into lower-voltage power, and goes out through multiple wires to about 20 Hydro Ottawa substations, which in turn feed power into communities and, eventually, into every single home in Ottawa.

If the rest of the city was going to get power, the brains at Hydro One were going to have to build a different kind of bridge between the Hydro One and Hydro Ottawa networks.

"We needed to find a way to use the infrastructure that was there to accept power, and get it back out again," Bradley said. There wasn't exactly a single "Ah ha!" moment, she said — it was more like a puzzle that different people worked on.

The solution was to repair a piece of equipment that conducts electricity, called a busway, and MacGyver it to allow power to come in from other sources, do a sort of loop-de-loop around the busway, and then get shot out of Merivale toward Hydro Ottawa's substations.

There was no guarantee it would work. And this sort of workaround is unusual at the best of times, let alone given the Merivale station's sorry state.

3rd time's the charm

By Sunday morning, Hydro One thought they could do it and told Hydro Ottawa to expect a power-up around noon.

But Hydro One kept running into snags, finding more repairs to do. Noon turned into 4 p.m., which turned into 7 p.m.

"It doesn't come, it doesn't come, it's excruciating," recalled Conrad of Hydro Ottawa. "It's causing a certain amount of grief — we still have 77,000 customers without power."

On Saturday morning, Hydro Ottawa CEO Bryce Conrad was warning of a 'multi-day' power outage lasting into the week. (CBC)

Then, around 8:30 p.m., the power started to flow into Hydro Ottawa's system. They decided to flip the switch for Longfields station, and it worked, at least according to the command centre controls. The immediate responses on Twitter told them it worked for customers, too.

"It's borderline euphoria at that point," Conrad said.

Then, one by one, power flowed to another dozen substations to the south and west, with Twitter announcing the lights coming on from Rideau Heights to Woodroffe. By 11 p.m. Sunday, most homes had power.

What's next

There were still about 3,900 homes without power as of Monday evening. Those may be among the most difficult to repair, with work needed on individual lines into homes damaged by fallen trees and high winds.

The system is working at full capacity, which isn't ideal. Conrad pointed out it's lucky we're not experiencing a heat wave, because the system couldn't handle air conditioners. And another severe weather incident in the coming days could wreak havoc on the system.

Hydro One won't know for a while what it will take to fully restore the Merivale station, Bradley said, but it's taking steps "to make it more resilient every day."

Still, the short-term fix for the past weekend's worst-case-scenario event is nothing short of a feat of engineering under pressure.

"On Saturday morning, what I was being told was, 'This is bad — this is really, really bad,'" said Conrad. "So to be in a position a little more than 48 hours later where we can light up most of the city is a pretty good feeling."