Transformer failure at Beilen substation causes large Drenthe power outage

What happened

At about 18:15 on a Friday evening, a 110 kV transformer at the transformer station in Beilen, Drenthe, dropped out. The transformer converts high-voltage supply from 110 kV to 10 kV. The failure cut power to more than 20,000 addresses. According to Enexis, the grid operator, repair crews were on site at Beilen and were working to return the transformer to service. Enexis expected to restore supply from about 20:15 that evening. The company said the cause was difficult to establish and that it would carry out an investigation, although its spokesperson doubted that the root cause could be fully identified.

Contributing factors

Not reported. Enexis described the cause as difficult to determine and said an investigation would follow.

Lessons learned

1. Keep spare or mobile transformer capacity for critical 110 kV to 10 kV substation transformers, so that a single unit failure does not leave thousands of connections without supply.
2. Record protection trip data and transformer condition monitoring data at the moment of failure, so that the root cause can be established even when the fault is hard to trace.
3. Plan restoration routes and interim supply switching in advance to shorten outages while a failed transformer is repaired.

More lessons on electrical protection and isolation, detection and monitoring, outages, backup supply and restoration, from every incident on the register.

Source

drentsnieuws.nl