What's an 'arcing flash,' and why is it ruining your commute?

Riki Philogene was on his way to work on Ottawa's Confederation Line Saturday afternoon when he was startled by what sounded like a gunshot.

He and his fellow passengers on the westbound train froze, andas they approached TremblayStation, they heard the sound twice more.Then sparks began showeringpast one of the windows.

• 'Power loss' on 2 LRT trains leads to delays for riders Saturday

"When we saw the sparks, that's why we were like, OK, lets just leave the train.Because you don't know what's going to happen next," Philogene toldCBC.

LRT riders shaken by loud bangs during Saturday trip

5 years ago

Duration 0:54

Riki Philogene was on an LRT train on Saturday when he heard several loud noises, followed by what he describes as sparks coming from somewhere on the vehicle's exterior.

Meanwhile, nine stops to the west,Melanie Grant stoodon the platform at Tunney's Pasture station, waiting for a train.Suddenly, she spotteda flame flickering where the arm atop a stationary train across the tracks met the power cableabove. She and the other people on the platforms edged away nervously, unsure what was about to happen next.

"I mean, we were told there would be growing pains and stuff, but I wasn't expecting to stand on the platform and think, oh, what if that explodes?" Grant said.

Since those incidents on Saturday, city officials have said emphatically that the public was never in danger from what they and Rideau Transit Maintenance (RTM) are calling "arcing flashes."

Wet weather to blame

Arcing flashes happen when the arm that extends from the train, called the pantograph,loses contact with the power cable above, or the catenary. Thatloss of contact is what causes the loud bang and the sparks, and causes the trains tolose power.

The phenomenon is common in train systems with overhead electrical power, according to Troy Charter, the city's director of transit operations. But the issue has only been causing LRT delays since late December, and first came to the public's attention during a particularly long delay on New Year's Eve.

At the time, city and LRT officials blamed a buildup of dirt on the electrical components of the trains.

"This is something that with proper maintenance should not have occurred," Charter told the city's transit commission justlast week. In response,RTMassured commissioners it hadstepped up efforts to clean and inspect the trains, and the problem seemed to have been resolved.

But two days later, during Saturday's snowstorm, it happened again.

"The vehicles appear to be more prone to these failures during wet or inclement weather," the city's transit manager, John Manconi, wrote in a memo to council Monday.The root cause of the issueis still under investigation by RTM, Manconi wrote.

Trains damaged

While Manconisaid he recognizesthe incidents cause inconvenient delays for passengers, arcing flashes are actually a sign the system is working properly. Like a circuit breaker in your home, the trains are shutting down as a defence mechanism against damage from irregular voltage.

The trains often do sustain damage and require repairs after arcing flashes.Such was the case on New Year's Eve, when officials described what looked like a burn mark on the train's roof. They also replaced some of the electrical components out of an "abundance of caution," Rideau Transit Group CEO Peter Lauch told the transit commission last week.

In other cases, the required repairs are more substantial, which contributed to this week's ongoing train shortage.

The city has promised torelease more information about any further measures needed to fix and prevent arcing flashes once they're confirmed by RTM.