Yellowknife
NT (March 4, 1999)
A major
repair program to replace 270 defective cable splices on the 140 –km
Snare hydro line got underway in late February, says the NWT Power Corporation.
The project, estimated
to cost up to $5 million, is deemed urgent by the Corporation to restore
the line’s safety and reliability. It connects Yellowknife and
Rae Edzo with 30 megawatts of hydro generation from four plants on the
Snare River.
The Corporation
became aware there may be a problem last winter, when two splices showed
signs of failure. Metallurgical tests conducted over the summer on a
random sample of 16 more splices showed the problem was likely consistent
across the entire system, and prompted the decision to proceed with
the repair. (The problem is unrelated to interruptions caused this past
winter by frost build-up on the power lines).
The cable splices
are aluminum metal tubes that connect strands by heavy electrical conductor
cable. During installation, these tubes are hydraulically compressed
to grip the cable ends. The tests showed that none of the sample splices
had been compressed to design specifications and could, over time, allow
the cables to separate.
A worst-case situation
could see a sudden, complete failure of a splice. The resulting whiplash
effect could collapse entire sections of the line’s 368 steel transmission
towers. Repairs would take months, and be extremely expensive, as the
City and Rae Edzo would be powered almost entirely by diesel generation.
“The loss of
this line would cut our electrical supply for up to a year”, said
Rick Blennerhassett, Vice President of Operations for the Corporation.
“Because the hydro supply is absolutely vital, we can’t afford
to put our system, and our customers, at that risk”.
“We are convinced
that the splice problem has reduced the margin of reliability and safety
to a point where we have to take action”.
The NWT Public Utilities
Board has agreed the project should go ahead on reliability and safety
grounds, but has deferred any decision on how to allocate the cost.
That issue will be decided during public hearings, when the Corporation
files its next General Rate Application likely in early 2000. The project
could impact Snare system power rates to Yellowknife, Rae Edzo and Dettah
by between 1.8 and 2.2. per cent.
The line was built
in 1989 at a cost of $22 million, replacing a smaller, wooden pole line
that dates back to 1948. Part of this older line will be restored and
used to relay power from Snare while the newer line is repaired.
The project will
be conducted in four phases over the next 15 months. More than 60 per
cent of the cost will be spent on services in the Yellowknife economy.
Under direction of the Corporation, several local firms, and one Alberta
company specializing in transmission lines, have been contracted to
handle helicopter, expediting and winter road clearing.
