Finding the power grid’s groove

Power outages have almost become an everyday occurrence for Yukoners and their businesses. In the last eight days, we've had three of them.

Power outages have almost become an everyday occurrence for Yukoners and their businesses.

In the last eight days, we’ve had three of them. The first, on December 10, lasted for more than 30 minutes and shut down the southern Yukon grid.

Then, on Saturday morning and Monday evening, the power went out again. This time the outages lasted a few seconds and only affected parts of Whitehorse.

There’s been at least seven unplanned outages this year, according to brief survey of news reports.

That’s coming off the heels of a busy 2008, when the lights went out 35 times. Half of the outages were caused by faulty equipment, the rest were caused by nature.

So why do we have so many outages? Why do some last hours while others last seconds?

And, more importantly, is it the fault of our two power utilities, the Yukon Energy Corporation and the Yukon Electrical Company Limited, or are the outage unavoidable facts of the Yukon’s tiny, isolated power grid?

It’s a bit of both.

In the last several years, the grid has been pushed to its limit, adding unexpected wear and tear to aging electrical infrastructure.

In March, Yukon Energy president David Morrison admitted the grid hadn’t been modernized in anticipation of the increased load demand from the Minto mine, big box stores and increased domestic electricity use.

“Hopefully, we’re at a point where we’ve got most of these (repair) issues dealt with and we hit the peak last year,” Morrison said back then.

“We’re still trying to play catch up.”

Part of the trouble is the grid itself.

But to understand why, you have to step into Mike Sage’s shoes for a day.

Sage is a Yukon Energy control centre operator.

He sits at the centre of the grid’s nervous system, 12 large computer screens towering over his desk.

The screens actually represent one big computer, called SCADA, or Systems Control and Data Acquisition.

“The control centre operator is the first point of contact if anything goes wrong,” said Guy Morgan, the control centre’s leadhand and Sage’s boss.

Those screens display everything from the output of a diesel generator in Faro to the water levels at the Aishihik hydro dam.

Most of the time things run smoothly. Sage’s job is to match power generation with power demand.

During his 12-hour shift, Sage can raise or lower the massive semicircular desk if he wants to sit or stand.

He can turn on a bit of music to pass the time, or he can talk a bit on the phone.

“There’s only one phone here that isn’t recorded so the guys can talk to their wives, or whatever,” said Morgan.

The rest are recorded so no one can deny making a mistake, he said.

And when an outage happens, those other phones start ringing.

One is for people to report outages. The other is a direct line to Yukon Electric.

And if those phones don’t tell him something is up, his screens definitely will.

An alarm screen will list inconsistencies on the grid.

Sage has to figure out if the problem is a faulty generator, or a problem in getting power to a resident’s house – in other words, transmission and distribution lines.

“It’s always a big balancing act here,” said Morgan. “You have to know what you lost and you have to know what you need to pick up.”

It’s the same with an outage – calculating power generation against demand – it’s just at a more stressful tempo.

Sage must match the frequency of the generators – hydro or diesel – with the power grid frequency.

But before that makes any sense, we need to step back a little bit.

At the start of every shift, Sage and his fellow operators forecast what the power demand will be that day.

Temperature is the biggest factor, and the peak is usually between 5 and 6 p.m.

“The streetlights are going on and everyone is firing up their stoves,” said Sage.

Once Sage knows what he needs, he has to figure out how much he can get.

The Yukon’s grid depends mostly on hydroelectricity from its Whitehorse, Aishihik and Mayo dams.

On the southern grid, Whitehorse can produce 40 megawatts and Aishihik produces 30. Mayo provides five megawatts for the northern grid.

These generators turn the mechanical energy from falling water into electrical energy. The amount of energy produced by a generator is the difference between the top of the dam and the bottom, called the head.

Sage has to measure how high the water is to determine how fast it will flow through the turbines.

He can adjust the water’s power by playing with the switchgates along the Yukon River before the Whitehorse dam.

He can also dump water from the dam’s reservoir, Schwatka Lake, and do the same at the Aishihik facility.

Once Sage knows how much he can get, he needs to assemble the right amount for the grid.

A generator’s output isn’t determined by its speed. In fact, Sage wants them to spin at the same frequency – 60 cycles a second.

It’s the North American standard for generators. In Europe, the standard is 50 cycles a second.

Rather, electricity is produced by rotating a metal rod attached to the turbine, creating an intense magnetic field.

If the water is pushing through the turbines too fast, Sage has to play with the magnetic field to add resistance and bring it back down to 60 cycles a second. If the water eases up, Sage does the opposite.

That force pushing against the magnetic fields determines the generator’s output.

Then there’s the tricky part.

“We’re not connected to the North American grid – we’re on our own,” said Morgan. “So the way we generate power is based on time.”

Sage can tell whether he’s producing enough energy for the grid by companying the frequency with an ultra-precise GPS clock.

If everything is perfect, the generators are spinning at sixty cycles a second and the difference between the clock and the “line time” is nothing.

If the generators aren’t producing enough energy, the grid’s cycle falls below 60 and a minus sign appears on Sage’s screen. If they’re producing too much, they go over sixty and a plus sign appears.

“The plus seconds are seconds the grid has to spare – it’s making more energy than needed,” said Morgan. “The minus seconds are seconds the grid is falling behind on – it’s not doing as many cycles as it needs.”

Operators must stay within 10 seconds.

“We usually do a little better than that,” he said.

Staying as close as possible to zero difference is key – it determines whether there’s enough energy on the grid.

“Right now, (the load demand) is coming down,” said Sage.

“We know people don’t have that many lights on and the lunch hour is over,” he said.

During a tour of the control centre, the difference between the GPS clock and the line time is plus five seconds – there’s more energy being produced than needed.

“I can tell by that frequency that I’m high,” said Sage.

He’ll lower the output of the generators to get closer to 60 cycles a second.

That balancing act is what Sage does pretty much all day.

“You get into the groove here a little bit and you know what the load’s going to be,” said Morgan.

And it’s risky to turn generators up or down too quickly.

“There’s always a compromise between response and stability with hydro units,” said Morgan. “If you react instantly, it’s typically not in a very stable and steady state.”

Keeping that in mind, there are basically two types of outages.

The first is caused by losing a generator. The second is caused by losing demand.

“If we lose generation, the frequency goes down,” said Morgan. “If we lose load, the frequency goes up.”

In other words, if a hydro turbine shuts down there’s not enough power on the grid and other generators aren’t matching the need.

If a tree falls over a transmission line, the grid loses demand and the generators are spinning too fast.

One of the big problems with the Yukon grid is its dependence on Whitehorse’s fourth generator.

It can produce up to 19 megawatts in the summer and 21 megawatts in the winter.

And it’s the only generator that runs 100 per cent of the time with the exception of maintenance, said Morgan.

Its governor broke last fall during a Thanksgiving weekend outage, and it has already caused multiple large-scale outages this year.

Most of the time, the grid keeps spinning reserve to replace any sudden generation loss.

But the reason generator four’s breakdowns are so devastating is because there is nothing large enough to match it; there’s no backup.

During the tour of the control centre, there was enough spinning reserve on to handle a diesel-generator breakdown.

If one did stop working, you’d get a brief blackout while other generators increased output to return grid frequency 60 cycles a second.

The other kind of outage are load outages. That’s when something happens – a raven, or fallen tree –

to the transmission or distribution systems.

These usually just cover a neighborhood, but sometimes they can have what’s called a cascade effect on the grid.

If a transformer faults, there’s too much power on the grid and things begin to go badly.

Sometimes there’s a domino effect, and the extent of the blackout is determined by protective devices on select transformers and grid substations, which are designed to contain such events.

If a grid is set to trip too easily, it can cause needless outages every time a branch, bird or squirrel touches a line.

If a grid is not protected enough, the outages can cause more damage.

So Yukon Energy must constantly evaluate and upgrade those system protections to suit new needs in power-hungry neighbourhoods.

Such system studies are complicated, expensive affairs that require measuring load changes on the grid.

Yukon Energy is expecting its latest study to be finalized soon.

“That’s on its way,” said Morgan. He didn’t know the exact release date.

Contact James Munson at

jamesm@yukon-news.com

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