You Asked, We Answer: What caused Saturday’s transmission line outage?

You Asked, We Answer: What caused Saturday’s transmission line outage?

Power outages are inconvenient and frustrating—especially when they happen on a sunny Saturday morning. Yesterday (March 9, 2024), over 45,000 customers lost power across the province. Although Thursday and Friday had brought a freezing rain storm, by Saturday, the weather was calm and clear, which had many of our customers wondering what happened. We asked Jill Searle, Director of Control Centre Operations, to explain this weekend’s transmission line outage and answer your most asked questions.

Why did the power go out?

Significant ice build-up on the transmission line connecting us to New Brunswick caused an outage on the line. When an interruption on this critical line happens, our system automatically enacts an emergency procedure that interrupts just enough electrical load to stabilize our system. This is what resulted in the outages you experienced on Saturday. Once the tie to New Brunswick was stabilized, power to our customers was carefully restored in groups to avoid a surge on the grid.

If the issue was with the transmission line to New Brunswick, why did we lose power in Halifax or Cape Breton?

The emergency procedure interrupts the electrical load in the areas that are using the most electricity—like in HRM and Sydney. This is the most efficient way to stabilize the grid. We were able to quickly restore power to most impacted customers in less than an hour.

Why are we bringing in power from New Brunswick? Can’t you make enough electricity from our generating stations in Nova Scotia?

While we have enough power generation within the province to supply all of Nova Scotia with electricity, it is often economical to import power from New Brunswick. We have a responsibility to provide you with power at the lowest possible cost, and so we often import electricity from our neighbours in New Brunswick.

Why didn’t you provide notice that these outages were coming?

Whenever possible, we notify our customers when we know there is potential for power outages. In this case, it was an unplanned situation, and the outage was an automatic emergency response. It meant that unfortunately, we were unable to provide advanced notice.

How are you going to prevent this from happening again?

We’re in the process of building a new transmission line to New Brunswick—we call this the ‘reliability tie’. This line will reduce the likelihood of power outages like this from happening as a result of future ice storms.

While this type of power interruption is uncommon, the automatic systems performed as designed to protect the electrical grid, ensuring it could be stabilized quickly. We thank our customers for your patience as we worked to safely restore power.

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