On this day 30 years ago (May 5, 1995), both units at Comanche Peak Nuclear Power Plant tripped after an electrical fault in the 345kV switchyard.
The unexpected culprit? A charred Great Blue Heron found at the scene.
At the time, both units were operating at full power. A fault occurred ~4 miles from the plant on one of five 345kV transmission lines.
Neither the primary nor backup relays cleared the fault. As a result, the other 4 lines & both units fed the fault—until everything tripped.
What happened next:
✔️ Both reactors safely shut down
✔️ No loss of offsite power to safety buses
✔️ EDGs didn’t need to start
✔️ 138kV remained energized
There was no weather involved. Just one bird… with a very bad day 💥
Why it matters:
This RARE dual-unit trip became a reference case in PRA.
It highlights how wildlife can impact critical infrastructure—& why even the best systems must account for unpredictable environmental factors. 🌿
Happy 30th to one of the weirdest, most instructive nuclear trips in U.S. history.
Cheers to redundant safety systems, & vigilant ops teams!