Underground transformer explosion causes widespread power outage in Halifax

What happened

A transformer located in an underground vault on Barrington Street in downtown Halifax exploded and caught fire, igniting other materials in the vault. The explosion caused a power outage affecting more than 8,500 Nova Scotia Power customers at its peak. Smoke travelled through underground conduits and sewer pipes into nearby buildings, triggering fire alarms and prompting fire crews to evacuate people from buildings on Barrington Street. Part of the street was closed between Sackville and Prince streets.

Firefighters had to wait for confirmation that the vault was de-energised and grounded before they could enter and extinguish the fire. The fire was brought under control by around 9:30pm. Power was progressively restored to customers, with the final connections completed by around 5:30am the following morning.

Contributing factors

The fire occurred within an underground electrical vault, and smoke spread through electrical conduits and sewer pipes into surrounding buildings before the fire was contained.

Lessons learned

1. Underground vault fires require verification that the vault is de-energised and grounded before crews can enter safely.
2. Smoke from underground electrical fires can spread through conduits and sewer pipes into nearby buildings.
3. Utilities need rapid feeder switching plans to limit outage size during vault fires.

More lessons on design, standards and commissioning, spacing, layout and fire spread, outages, backup supply and restoration, from every incident on the register.

Not yet known

• Cause of the transformer explosion
• Transformer model and age
• Cost of repairs and outage

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Source

cbc.ca