That Sunday night power flicker explained

Image of Vancouver Yaletown at night

An electrical fault in our transmission system caused brief Lower Mainland outage

For most, it was a barely detectable blip in the dining room light or on the TV. For others, it was a brief lights-out experience on a local ski hill, complete with a temporary halt to the chairlift they were on.

No doubt, Sunday night's electrical fault noticed by customers in areas around the Lower Mainland was unusual and rare. But despite a flurry of questions as to what happened, it's not cause for any concern.

"A lot of people might experience a flicker once or twice a year on the [power line] that supplies their house,"explains BC Hydro's Paul Choudhury, who manages operations of our transmission and distribution system. "But this one was a particularly different one, because it happened on the transmission system. That's where we bring the power in from our high-voltage provincial grid for distribution across the Lower Mainland.

"Ultimately, thousands of customers receive power from transmission lines, so when something happens, it can affect a lot of people. “

Within a fraction of a second after the fault was detected by the electrical system, it was isolated and power was restored by redundant power lines in our system. That's what most customers in the Lower Mainland experienced, but there were others who had their power out for 10 seconds or longer, as protection systems installed by businesses with sensitive equipment 'tripped'."

"Those protection systems may have shut down their motors, or shut down their sensitive loads," says Choudhury in explaining how some outages were longer than a flicker. "That would be the time it took for them to start their loads up. Or they would have phoned us at our control centre to say 'What happened – is there a problem with the system?' We'd say 'No. Go ahead and start your load up.'"

No lengthy power outages

“When we plan the electrical system, we plan it to be redundant," adds Choudhury. "On this high voltage level, we can usually lose one of our lines – one of our sections of a substation – and still continue to supply power to our customers. Everything worked the way it was planned to work."

Choudhury says that because the blip was seen by so many amid calm weather, it might have come as an unsettling surprise.

"It's unusual for an event like this to happen that's not precipitated by something else," he said. "It's usually an earthquake, a fire or a windstorm that blows something at one of our substations. But in this case, there was no precipitating event. It was a piece of equipment that let go that shouldn't have, and we're investigating why that happened."