Lightning is some nasty stuff. Luckily, it doesn’t have a very long lifespan. [BigClive] decided to tear down an 11KV lighting arrestor used in power distribution systems. The fiberglass core has silicone rubber water-shedding disks that make the unit look sort of floppy, but inside is some serious hardware.
To protect the circuit, metal oxide varistors shunt high voltage from a lightning strike to ground as you’d expect. The interesting part is how the device deals with failure. It would be a disaster if the device shorted the 11KV power line to ground for any length of time due to a fault. To prevent that problem, a resistor heats up when struck by lightning and triggers an explosive charge that disconnects the ground wire and releases a flag to indicate the failure.
[BigClive] triggered the charge in the video below. So if you like to see things explode in a bucket of water, you’ll enjoy the video.
Amazingly, this isn’t the first lightning arrestor tear down we’ve seen (although the embedded link is dead). However, it seems most hackers don’t want to stop lightning, they just want to photograph it.