Nova Scotia Power explains Monday’s transmission issue, outages due to freezing rain

Tens of thousands of Maritimers were without power for part of the day Monday following the latest round of rain and freezing rain in the region.

In Nova Scotia, there were 56,000 customers without electricity early in the morning. At that time, Nova Scotia Power said the outages were due to a "transmission disruption.”

The utility later said the significant outages were related to its transmission tie to New Brunswick.

Matt Drover, the senior director of transmission and distribution operations for Nova Scotia Power, says freezing rain caused ice-build up on distribution lines in the northern part of the province.

“And just after 5:30 a.m. (Monday) morning, we did lose that main tie to New Brunswick due to ice build-up and that led to the significant customer outages that we had,” he told CTV Atlantic’s Todd Battis.

Drover says there is a 345,000-volt line and a 138,000-volt line running to New Brunswick.

“We also have the Maritime Link that connects us to Newfoundland and when we lost that main tie to New Brunswick that did separate us from the grid at that point.”

After the connection was lost, Nova Scotia Power customers had their consumption reduced in order to stabilize the grid.

Drover says the utility has “very detailed procedures in place” if the system does become unstable.

“We are able to reduce the load very quickly and then, once things have stabilized, we are able to bring those customers back on. So that whole process was about two hours, some locations, a little bit less than that, and some locations just over, but roughly two hours to get everybody back on.”

Most of Monday morning’s outages were in the Halifax area, which is part of Nova Scotia Power’s plan when power needs to be reduced.

“We look at areas that have the most customers in a central location, and we try to geographically spread that throughout the province as well, so the Halifax-HRM area had some areas that were affected, as well as the Truro, New Glasgow and Sydney areas,” says Drover.

It has been a mild winter in the Maritimes, with few snow events that are typically seen in the region in mid-January.

Drover says windy and rainy conditions pose different, and sometimes more severe, problems when it comes to restoring power.

“With snow or wind events, mostly what we see are trees coming down onto our lines and once the weather had passed through, we can remove those trees and get the power back on relatively quickly,” he explained.

“And some cases, depending on how big the damage is, with ice build-up, it is significant build-up on the trees that hangs in there, so the ice continues until it melts. So in some cases we have to physically remove the ice, or in other cases, if the ice can’t be removed, the temperature needs to warm up for that ice to be removed and then the power to be restored.”

Drover adds that pruning trees “always helps” reduce the potential impact of branches on power lines.

“With the customers that are off right now in the northern part of the province, that ice build-up on the trees that led to the distribution outages, continued vegetation management, removal of trees, getting them further away from lines would definitely help with that.”

As of 9:15 a.m. Tuesday, 62 Nova Scotia Power customers were without electricity, with the largest outage in East Mapleton, just outside of Springhill, N.S. It’s estimated that power in that area will be restored by the afternoon.