True story, I was installing a CT in Atlanta. The clinic was in an office park that had been an old school of some sort. There was a power distribution room for the whole complex.
The complex maintenance people sent a guy to dust and sweep out the power room. The large wall mounted power panels had dust on the tops and… metal slug washers (punch outs).
The guy accidentally knocked one of the metal slugs through the vent slot in the top of a large 480vac distribution box. This shorted out the entire complex. I heard the “boom” in a closed room 80yds away.
I raced up the distribution room to see what happened. This guy walks out of the room looking shaky. I asked “Are you okay?”
The only thing he said was “I Quit!” in a stuttering voice...
I helped move an old X-ray system. I had a panel off and told the other guy to flip the breaker on. When he did there was a huge bang, a flash of light and smoke. I said to turn the breaker off, he said he couldn't because it had blown out of the breaker panel.
Apparently, there is a difference between 220v single phase and 220v two-phase. He missed that detail in the plans.