pic: Not the end of the Rainbow, but ....

[skimoose]

This was the lightning storm that rolled through on 7/28/06. The driveway was asphalt, but I have seen similar damage to concrete as well. What looks like metal in this mess is actually more like a crude glass called a fulgurite. The line conductor an aluminum alloy known in the trade as AAAC (aluminum alloy - aluminum core) with such a low melting point I'm pretty sure most of the conductor vaporized. The fulgurite is glass formed as the silicas in the underlying soils melt in the intense heat, the bubbles are cooled glass that was forced to the surface probably by escaping gases.

This particular line was protected by a 65 ampere k-speed fuse. K speeds are the fastest melt time fuses available. Unfortunately, this was a high impedance fault and it took several minutes for the fuse to clear this arcing fault. I'd hate to guess at the initial temperatures (3,000-4,000F?), it looked like molten glass or lava (cherry red). The local fire department emptied 300 gallons of water on the asphalt after power was cut, and all they accomplished was to make a lot of steam. I revisited the site 6 hours after the fault, as the crews were making final repairs and the asphalt 3-4 feet from this burn was still soft to walk on (probably 150F)

Other than the downed line and loss of power, the homes in the area suffered no damage. The damage was localized in this case. Wires down like this don't tend to "dance" around, they just lay there and burn like a giant arc welder.

What's even scarier is this was the smaller of two lightning strikes. The larger strike about one quarter mile from this site cut a major three phase circuit down, and left a flaming 2 foot diameter, 4 inch deep fulgurite crater in the middle of a major asphalt road. Unfortunately, I didn't get to photograph that strike. The public works crew had dug up the road and patched it before I got there.