A major test of the troubled transmission line from Labrador to the Avalon Peninsula scheduled for Thursday knocked out power to thousands of customers shortly after 10 a.m.
Newfoundland and Labrador Hydro said Wednesday the test could cause power failures for some customers.
Testing of the Labrador-Island Link, which carries electricity from Muskrat Falls in Labrador to Soldiers Pond, will run at a higher-than-normal power level of 675 megawatts as part of the link's commissioning process, according to a press release Wednesday evening from Hydro.
Operating the link at a higher level than normal will test whether the link's software is working properly, according to the company.
The increased output had the potential to trip some pieces of equipment, Wednesday's release said, and cause power outages in what Hydro calls an "under-frequency load-shedding event," which is when Hydro cuts power to some customers to balance out the system during an unexpected surge of power.
Newfoundland Power initially reported outages across the Avalon Peninsula, the Whitbourne area, the Burin Peninsula, Clarenville and the Bonavista Peninsula, the majority of central Newfoundland and the Corner Brook and Deer Lake area on the west coast.
Later in the morning, all unscheduled outages were over.
Similar outages happened earlier this month, when a power imbalance created during testing of the Maritime Link caused about 57,000 customers to be without power for around 16 minutes.
Any outage connected to tripping equipment should last less than 30 minutes, Hydro said, adding updates will be regularly posted on its social media channels.
A similar test is scheduled for next week.