BC Hydro talks power failure

After the chain reaction of weather-related problems behind last December's day-long power outage, the province's power utilities are assuring Tumbler Ridge that fixes are being made to prevent it from happening again.

At last Monday's (Feb. 8) policy and priorities meeting, a sizeable contingent of seven B.C. Transmission Corporation (BCTC) and BC Hydro personnel provided the details of what went wrong.

"BCTC views this incident as very serious; our worst nightmares came to fruition on this incident," said Larry Haffner, BCTC manager of asset program definition. (BCTC manages and operates the substation and transmission line adjacent to Highway 29). The root cause of the power outage was a wiring error on work done earlier in 2009, which caused a compressed air system problem.

That resulted in the power outage at 4 a.m. on December 14. Efforts to repair those components were hampered not only by weather dipping below -30 C, but by a lack of supplies, too much snow on an access road, and an urgent family matter for one of the BC Hydro repairmen. After some delay, BC Hydro crews arrived in the area but couldn't make it through the snow to reach the substation, located roughly 10 kilometres northwest of Tumbler Ridge.

A contractor from Chetwynd was called in to clear snow, but a new problem arose at 10:30 a.m.: an electrician learned his mother had died, and had to leave the work site. To send in a replacement worker, BC Hydro needed to rent a vehicle in Dawson Creek, as the cold weather meant their available service vehicles could not start.

Over the course of the day, the repair crew had to use a diesel generator to provide a heat source and electricity supply to the control room's substation, and had to find a source of compressed nitrogen with which to re-pressurize the breaker. In all, Tumbler Ridge went through 14 hours of outage before power was restored at about 5 p.m.

To address the problems encountered during the winter outage, BC Hydro community relations manager Dave Conway laid out planned upgrades that would make the substation among the most reliable in northern B.C.

Since the substation was actually designed to withstand temperatures of -50 C, a full substation review will be carried out to assess its resiliency to extreme cold weather, he said. It will also receive a larger standby generator, and the substation's transformer capacity will be improved.

The utility will also try to add Tumbler Ridge snow removal contractors and compressed nitrogen suppliers to their procurement list, said Conway. Because power is supplied to Tumbler Ridge via a radial line feed directly from the Peace Canyon Dam, the district remains vulnerable to outages caused by lightning strikes. That was the cause of the 26-hour power loss that started on Feb. 11 last year.

Falling trees can also pose a hazard to the line, and BCTC personnel at the meeting explained they'll spend $25,000 on pruning work this year. That comes after BC Hydro and BCTC jointly spent $400,000 on vegetation management in the community and along the power corridor last year.

Councillor Kelly McManus had concerns with the response time to the power outage, and asked what it would take to station some BC Hydro personnel in Tumbler Ridge. Conway replied that two source outages per year could not justify stationing a BC Hydro employee in the district, and noted BC Hydro electricians from Hudson's Hope can also be deployed to Tumbler Ridge.

Asked by Councillor Doug Beale whether the proposed wind energy projects in the region could supply power to Tumbler Ridge in the event of an outage, Conway explained the unconstrained voltage and frequency make power from wind turbines unsuitable for supplying directly to customers. But electricity from a thermal-based power source in the district could provide stable power.

"A biomass cogeneration plant would probably be ideal," said Conway. Tumbler Ridge would also need a back-up supply agreement with BC Hydro in order to switch to local power during an outage, he said. The next planned power outage in Tumbler Ridge will be due to a wind project. The district may be without power for up to eight hours sometime in June, when BCTC connects the Dokie Ridge Wind Project to the grid. The project, located north of Chetwynd, is expected to be up and running by early 2011.