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

What happened

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.

Contributing factors

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.

Lessons learned

1. A substation explosion can lead to a second fire days later in a hydro vault, so operators should keep monitoring after the first event.
2. De-energising the station before investigation allowed quick suppression of the second fire with fourteen fire trucks.
3. Power rerouting plans prevented customer outages from the second fire at the damaged site.

More lessons on detection and monitoring, fire suppression and firefighting, from every incident on the register.

Not yet known

• Cause of the first transformer explosion
• Model and age of the four transformers
• Amount of mineral oil that reached the Humber River
• Duration of the investigation and downtime

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Source

cbc.ca