LRT wires 'melted' during January ice storm, transit commission hears

An accumulation of ice during a storm in early January triggered a series of failures that knocked Ottawa's LRT system out of commission for days, the city's transit commission heard Thursday.

During the storm, which began on the evening of Jan. 4, ice began to form along the overhead cable system that powers the Confederation Line.

According to Richard Holder, the city's director of engineering services, the buildup was particularly heavy in a section near the Rideau River, between Hurdman and uOttawa stations.

The Confederation Line remained partially closed from Jan. 5 to the evening of Jan. 10, while crews laboured to de-ice the cables and remove immobilized vehicles, including rescue trains.

Storm pushed limits of system

The LRT's overhead catenary system is designed to handle 12.5 millimetres of ice accumulation. On the evening of Jan. 4, Environment Canada reported 4.3 millimetres of freezing rain per hour falling over Ottawa, Holder told commissioners.

"So we were already getting close to the threshold of our design," he said.

Even with the ice accumulation, the trains managed to keep moving until they reached the Rideau River microclimate, where the open water made for greater humidity — and heavier ice buildup on the overhead wires.

That led to significant arcing, causing bright flashes and sparks where the trains' pantographs — the roof-mounted apparatus that transmits power to the vehicle — lost contact with the overhead wires, halting the trains on a stretch of track between Lees and Hurdman stations.

When a recovery train was dispatched to help, its slow speed caused more problems, Holder explained. 

"The contact wires basically melted," he said, describing the single-strand wires that are suspended from the catenary cable by droppers.

"Normally, when a vehicle is moving fast and we get arcing, the arcing ... is spread out over a larger area. With the vehicles basically stationary, that arcing all occurred in the same section, creating a huge amount of energy, a huge amount of heat generated, and the contact wire melted."

Two rescue vehicles eventually became stuck, a spokesperson for the city said.  

On Jan. 6, crews were dispatched to remove the ice by hand along the entire middle section of the Confederation Line — a distance of more than five kilometres.

Workers also had to replace the damaged wires and perform safety checks that took days, Holder said.   

Heating wires, de-icing spray considered

Holder outlined several fixes that could potentially prevent ice accumulation from causing a similar multi-day failure.

A working group is looking at using antifreeze, similar to steps taken by the Toronto Transit Commission (TTC). Other ideas include better monitoring of the equipment and procuring diesel vehicles to rescue immobilized trains.

"If we have issues with the power supply such as what occurred in early January, then we cannot use an electric vehicle for recovery," Holder said. 

The group is also looking at the idea of equipping a maintenance vehicle with a special ice-breaking pantograph, as well as heating the cables to prevent ice from forming in vulnerable areas such as near the Rideau River. 

Since the Confederation Line opened three years ago, Holder said it has experienced ice accumulation more than 50 times without incident. According to the working group's analysis, LRT trains begin to break down when more than 6 or 7 millimetres of ice forms on the overhead wires.