The city has now figured out what disrupted the commute of thousands of Calgarians for a few days last week — a pantograph.

That’s the electrical connection on the roof of the C-Train that provides power.

C-Train service between Crowfoot and Dalhousie stations in the northwest was disrupted last Tuesday afternoon after an overhead power line came down.

"We really wanted to understand the root cause, rather than the secondary effects,” said Calgary Transit manager Craig Harper.

Electrical repairs

Workers do electrical repairs near Crowfoot Station after an overhead power line was damaged. (CBC)

A carbon contact strip, which acts as a smooth buffer between the pantograph and the wire electrical wire on the top of a train, was damaged and that caused the wire to be ripped down by the train.

"We are investigating whether the batch of strips had any issue with it that contributed to this failure."

The city is now inspecting seven C-Train cars that use the same carbon strips.

The disruption to service and repairs cost the city $175,000.