Old switch caused blackout
Calgary will spend $1M on fix after five-day ordeal
The city will spend an estimated $1 million to upgrade aging streetlight switches in the wake of an investigation that discovered one of the devices may have caused an explosion and fire last fall that left a large swath of downtown Calgary without power for five days.
While the suspect relay was reaching the end of its three-decade life, transportation general manager Mac Logan said the city had no program until now to replace the devices unless they failed.
“It’s very uncommon for a relay to result in a fire,” Logan said.
“In fact, this is the only occurrence of this nature that we have on record.”
Five thousand residents, 10,000 workers and 17 downtown blocks suffered through a blackout that began on the evening of Oct. 11 when area residents reported hearing small explosions and seeing blue flames shooting from a manhole near the intersection of 8th St and 5th Avenue S.W.
An investigation summary by the fire department released Friday said the extent of the damage to the content of the underground electrical vault beneath the manhole made it difficult to pinpoint the exact cause of the blaze.
But the report concluded the switch is the likely culprit due to the timing of the fire shortly after dark when a photocell would have triggered it to turn on the streetlights.
Scene examination also suggested the switch or contactor likely suffered arcing due to “carbon tracking or contact failure” that caused a fire to ignite.
“It is likely that this event could have occurred in any number of manholes containing relays or contactors as a result of equipment failure or aging,” the summary said.
“It would be recommended that a followup inspection of contactors of similar design and age be completed to minimize the possibility of future events such as this.”
Manufactured by Davis Controls, the mercury sensor relay was installed in 1986 along with the streetlights in the area, Logan said.
Officials with the Ontario-based firm did not respond to Herald queries about the recommended life of the device or whether there have been other incidents where a similar device had caused a fire.
There are approximately 10,000 relays throughout the city that control about 90,000 street lights. While devices in suburban areas are located on poles in weather-rated boxes, those downtown are all below grade in power utility vaults.
Logan said all the relays in the city core will be relocated from manholes to light poles to allow for easier access and fewer traffic disruptions.
“The nature of the equipment has changed and they’re easier to service up there,” he said.
Money for the work will presumably be found from a new $12.8 million capital request approved by city council this year that includes funding to replace “aging, unsafe or critical system components to meet safety requirements” for Calgary’s system of streetlights.
Maintenance of the system is currently done by a subsidiary of Enmax, although a recent study recommended the contract not be renewed when it expires in 2016 because there has been a “steady decline in performance” by the city-owned utility which has had a “historical monopoly” on fixing street lights.
The review for council noted that in 2006 over 80 per cent of repairs were completed within two days, but by 2013 only about 20 per cent were fixed within the same time frame.
The report said the city should look at outsourcing the service to multiple providers in hopes of getting better service through increased competition.
“It is crucial that the city identify and enforce performance measures against which to monitor success,” the review said.
“The contract should also provide penalties for failure to meet ... expectations.”
Gianna Manes, ENMAX’s chief executive, said the utility has always had a strong maintenance program.
“Enmax continues to inspect our wires and equipment in the manholes and any items of note are identified and addressed,” Manes said.
Until now, Logan said about 60 switches were replaced each year when they stopped working and neighbourhoods were either left in the dark or the lights stayed on.
Now, about 130 mercury relays beneath downtown will be replaced over the next six months.
“Our first step is just get rid of all these relays, Logan said. “It’s the fastest way to eliminate this risk.”