Lakefront Utilities says a faulty switch inside one of its substations caused the power outage in Cobourg.
In an explanation of the outage on Friday, the utility said its protection equipment detected the fault and shut down the affected equipment as designed.
Crews initially inspected distribution lines but found no visible damage, leading them to believe the problem might have originated on Hydro One’s system.
Rather than wait for Hydro One to complete its investigation, Lakefront Utilities attempted to restore electricity by transferring customers to a different feeder from Port Hope.
When that feeder also tripped, crews determined the fault was within Cobourg’s electrical system.
Further inspections and a review of customer reports did not immediately reveal the problem. Crews then developed a method to narrow the search by restoring power to sections of town one at a time and monitoring how the system responded.
That process helped isolate the location of the fault, which the utility identified as involving a switch inside one of its substations.
Lakefront Utilities also thanked residents who reported hearing loud bangs, seeing flashes of light or noticing other unusual activity during the outage.
The utility said those observations provided valuable information as crews worked to locate the problem.
The explanation did not specify what caused the switch to fail or provide a detailed timeline for the restoration of service.
