Transformer fire at Blount Street substation causes Madison, Wisconsin outage

What happened

In July 2019, a transformer at American Transmission's Blount Street substation on East Main Street in downtown Madison, Wisconsin, failed, resulting in an explosion and fire. Insulating fluid burned in the fire, producing a thick smoke column visible over a wide area. Shortly after the fire began, the local distribution utility de-energised the substation to allow firefighters access, which interrupted supply to downtown Madison customers. Distribution crews worked through the day and all affected customers were reported reconnected by early evening.

Transmission equipment at the connected East Campus substation was also damaged, although the distribution utility's equipment at that site was reported undamaged. The Wisconsin state environmental regulator supervised cleanup of the Blount Street site. Some insulating fluid burned in the fire, the remainder was pumped from the transformer over the following weekend, and an environmental contractor used a skimming method to separate dielectric fluid from firewater that had flowed from the substation.

American Transmission stated publicly that the fluid was a dielectric fluid commonly used for insulating electrical equipment, and the environmental regulator confirmed that it did not contain PCBs.

Contributing factors

Publicly reported information was limited. American Transmission stated that a transformer failure had occurred and that it was examining the transformer components to identify the root cause. No root cause was published at the time of reporting. The reported burning and release of dielectric fluid is consistent with loss of containment from the transformer, although the failure mechanism was not published.

Lessons learned

1. A transformer fire at a substation releases burning dielectric fluid that requires environmental cleanup, so retain a contractor and maintain contact routes with the regulator.
2. De-energisation of a substation to allow firefighter access interrupts supply, so agree switching sequences with the distribution operator in advance.
3. Damage can occur at an electrically connected substation, so include propagation to adjacent assets in fire risk assessments.

More lessons on worker safety and safe systems of work, fire suppression and firefighting, spacing, layout and fire spread, from every incident on the register.

Not yet known

• Root cause of the transformer failure
• Transformer model and age
• Exact downtime and cost of repairs

This entry is updated when these are reported. Get an alert for the next one like it.

Source

wkow.com