Second fire breaks out at Hydro One substation after earlier transformer explosion

An explosion occurred overnight at a Hydro One station near Finch Avenue West and Signet Drive in North York, Toronto, leaving about 35,000 customers without power at the peak of the outage. The blast ruptured transformers, which leaked mineral oil, with an unconfirmed amount reaching the Humber River. Three days later, a second two-alarm fire broke out in a hydro vault at the same station. Fourteen fire trucks responded, but crews were able to extinguish the flames quickly because the station had already been de-energised for the ongoing investigation into the first incident. No injuries were reported in either event. Hydro One said two of the station's four transformers were unaffected by the fire, and Toronto Hydro had already rerouted power so customers were not affected by the second blaze.

The second fire appeared to have been caused by an electrical or mechanical malfunction within the hydro vault, occurring while the station remained de-energised during the investigation into the earlier transformer explosion and oil leak.

1. Substations that have suffered a major electrical fault or explosion may remain at risk of secondary fires during the post-incident cooling and investigation period, warranting continued monitoring.
2. De-energising damaged equipment before an investigation is complete can reduce the severity of any recurring fire and speed up suppression.
3. Utilities should have contingency rerouting plans ready so a repeat incident at an already-damaged site does not cause further customer outages.
4. Oil leaks from damaged transformers near waterways should be assessed promptly for environmental contamination.

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