We had a lightning induced power failure years ago. Also had a bank of batteries and diesel generators to take over that failed to work. Seems the folks that maintained the UPS system monthly failed to disconnect the dummy load used for testing.....
Or my personal favorite from ATC. We religiously switched to the standby generator on the first Sunday of the month to make sure all was good, it always was. One day we lost power, generator fired up and all was good...... for a couple of minutes, then it went very dark and very quiet.
Seems the monthly startup / shutdown checklists made no mention of fuel quantity !!!