How an engineer kept a power failure from derailing a keynote speech

In his 2011 book An Engineer’s Alphabet: Gleanings from the Softer Side of a Profession Dr. Henry Petroski tells the story on page 22, under the heading of Backups and Redundancy. His keynote speech on success and failure in design began normally, but after about ten minutes there was an ominous hum, and all electrical power in the hotel ballroom went out.

Dr. Petroski continued without his PowerPoint slides for about five minutes. Then the projector came back on, and he ran through those missing slides. Power to the projector went off again briefly, but then it stayed on until he finished his speech. Later the emergency generators in the hotel restored the lights and some other power. What had happened? Where had the backup power come from?

City workers accidentally had hit some buried power lines. The engineer who organized the meeting had driven his truck to the hotel. He knew that his truck had an inverter powered by the battery that could provide enough AC power to run the projector. So, he drove his truck up onto the sidewalk outside of the ballroom. Then he scrounged three extension cords from around the room, and connected his backup power supply to the projector. The second brief outage was from someone having tripped over and disconnected one of the extension cords in the still dark ballroom.

The image of a derailed train is from Wikimedia Commons.