Power lines are dropping along the Labrador-Island Link, and N.L. Hydro can't explain it

Three sections of conductor wire along the trouble-ridden Labrador-Island Link have dropped to the ground since early December, and as crews continue their repair efforts, N.L. Hydro officials say they're still trying to find out what's causing the failures.

But the focus is squarelyon a rigging devicecalled a turnbuckle, a piece of adjustable hardware that secures the power line to the larger, four-foundation towers along the transmission line. These so-called "dead-end" towers account for about one of every 20 towers.

During a stretch of freezing rainfallsin December and early January, some of these turnbuckles broke, andnow Hydro personnel are scrambling to find out why, and what it might mean for the future of the link.

"We need to determine: are these failures weather-related? Are they component-related? What is the best plan of approach to be able to remedy the situation?" said Walter Parsons, Hydro's vice-president in charge of the Labrador-Island Link.

Details about the latest software and structural setbacks to hit the nearly $4-billion, 1,100-kilometrehigh-voltage transmission line from the Muskrat Falls generating station inLabrador to the Soldiers Pond terminal outside St. John's are contained in Hydro's monthly update to the public utilities board.

They reveal how challenging repairs can be when failures occur in remote areas, and why N.L Hydro believes it will require a robust backup system when the link, known as the LIL,is eventually commissioned and integratedinto the province's power grid.

In early December, a turnbuckle failed on a tower on the Northern Peninsula, near Hampden, and one of the link's two power lines dropped to the ground.

A contractor was hired to clear snow from a 72-kilometre access road, and the repair was completed on Dec. 12, nearly two weeks after the problem was discovered.

• N.L. Hydro proposing Bay d'Espoir expansion to meet electricity load growth

In late December and early January, a similar failure was discovered in the same area of the Northern Peninsula,and a third was found in southern Labrador. In all three cases, the power lines were coated with ice.

The turnbuckles are made of forged steeland are designed to withstand heavy loads, including ice buildup. So the broken turnbuckles are being tested in a laboratory, and Hydro has commenced an investigation that will also include outside consultants.

Parsons said it's not uncommon for failures to occur in the early years of operation of a new asset like the LIL, but he's not ruling out the possibility of having to upgradethe link's infrastructure in areas prone to freezing rain events.

"There may be some additional investments in the Labrador-Island Link," he said. "We don't estimate these are going to be massive investments. We're not talking about redesigning the Labrador-Island Link here."

The LIL comprisestwo power lines known as Pole 1 and Pole 2 and is capable of transmitting up to 900 megawatts. If one of the lines fail, the other line is designed to operate in overload mode, and safety stabilize the system.

The link is undergoing regular testing prior to final commissioningand has been routinely transmitting roughly 300 megawatts for use on the island power gridand for export to Nova Scotia via the Maritime Link.

The line failures have not resulted in widespread outages becausethe oil-fuelled thermal generating station in Holyrood, which has a capacity of roughly 500 megawattsand has been a key source of generation in the province for a half-century, is fully operational.

Meanwhile, LIL repairs are ongoing, and Hydro says the link is being taken out of service during the day to create a safer work environment for line crews.

• Gloomy Muskrat update reveals transmission testing hampered by vibrating condensers

The line failures are in addition to a setback that occurred in late November as a high-power test the final milestone before commissioning was carried out on the LIL.

On Nov. 24, Hydro and its contractor, GE Canada, attempted a 700-megawatt overload test.The test was initially successful, with Pole 2 successfully compensating when Pole 1 was intentionally tripped. But after just 44 seconds, Pole 2 unexpectedly tripped, and 58,000 customers in Newfoundland temporarily lost power.

Parsons said GE is working on a new version of the operating software, and another high-power test is expected to take place in February or March.

Despite all the setbacks, Parsons said,"This is the most confident that we've been."

It's the latest chapter in a troubled history for the Lower Churchill project, which was sanctioned by the provincial government a decade ago and has been plagued by cost overruns and schedule delays.

The 824-megawatt generating station at Muskrat Falls was commissioned in 2021, but ongoing problems with the control and protection software and the reliability and design of three large synchronous condensers at Soldiers Pond have delayed commissioning of the link.

Read more from CBC Newfoundland and Labrador