Short circuit in Ellwangen substation transformer sparks grass fire

What happened

At about 19:00 on Sunday 9 July 2023, a power cut affected about 15,000 households in Ellwangen and several neighbouring municipalities. According to the operator ODR, a short circuit in a voltage transformer at the Ellwangen substation was the cause. Oil escaped from the transformer and ignited on site. Smoke prompted a call to the fire brigade, which found only burning grass to extinguish and brought the fire under control quickly.

The substation is fenced, and the operator said no people were at risk. The operator activated a crisis team. Power was restored to the network after about 15 minutes, because all systems are staffed twice over and were fully tested before restart. The defective transformer was due to be replaced in the following days, which the operator said could be done without switching off the supply.

Contributing factors

The operator described the fault as a short circuit in a voltage transformer, which it called a normal defect of the kind that can occur where machines are in use. The oil that leaked from the transformer ignited on site and set fire to grass.

Lessons learned

1. Oil-filled instrument transformers at substations need bunding or containment so that any leaked oil cannot reach vegetation or ignite.
2. Keep vegetation cleared around substation equipment, because a small oil release can quickly become a grass fire.
3. Duplicate staffing and tested restart procedures allow supply to be restored within minutes after an equipment fault.

More lessons on maintenance, inspection and ageing assets, worker safety and safe systems of work, from every incident on the register.

Source

schwaebische-post.de