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

[Al Skierkiewicz]

Amazing what a little 7920 volts can do. I suspect it found it's way to ground through water in the cracks in the driveway? A lot of the molten mass is drive material and what lies underneath with a little wire through in for color? Great picture, Art! Took a while for the fuse to trip I bet. Is there any other localized damage from the wire dancing around?

[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.

[Al Skierkiewicz]

I forget you are in a different part of the country so ground conditions are different. Here in Illinois, I have witnessed down lines that dance as ground water repeatedly seeps close enough for arc over and the resulting steam burst throws the end of the line around. Not the kind of arcing people see on TV or the movies but interesting none the less. These are the kind of things that elelctrical workers are exposed to all the time that the general public knows nothing about. Risky business!
Was the line hit by lightning or just downed through some other storm related event? A few years ago, I was watching out my back door during a lighting storm when a 113kV line was struck a few miles away. An arc over occured in a yard behind my where the service line drooped low. Arcwas about 16 ft. to ground from the low spot on the line. I am very near the end of the distro for my neighborhood, only one transformer after my house before the end of the line. Everything between my house and the intial strike was tripped. A lot of fuses were replaced that night.

[skimoose]

Originally Posted by Al Skierkiewicz

Was the line hit by lightning or just downed through some other storm related event?

Both events I described were direct hits to the distribution system. There were lots of tall trees in the vicinity but I couldn't find any evidence of the strikes hitting the trees. One strike was a direct hit on the pole itself. The pole top was split with a 3" exit hole about a foot down from the pole top bracket which then discharged into the lower arm brackets.

[KenWittlief]

Personally I like huge thunderstorms. I assume everyone allready knows this: sound travels at approximately 1000 feet per second. When you see lightning and start counting off the seconds till you hear the thunder, you can measure how far away the lightning bolt hit the ground.

1 second is about one city block away. Half a second is 500 feet. When you get one of those you know something right in your neighborhood got hit!

If you see the direction of the lightning you might be able to go out after the storm and find the spot where it hit. Sometimes its easy to find, things like a tree with half the limbs and bark blown off one side!

Man... I'm missing out on fun storms like that here in Cali. All I get is the ground shaking under my feet... Which gives you quite a sense for the scale of the earth, feeling what is just a tiny movement of pieces of the crust....

[Jeremiah Johnson]

Originally Posted by 114ManualLabor

Man... I'm missing out on fun storms like that here in Cali. All I get is the ground shaking under my feet... Which gives you quite a sense for the scale of the earth, feeling what is just a tiny movement of pieces of the crust....

I'd rather have nasty thunderstorms and tornados than earthquakes anyday. I've seen about 5 or so tornados actually form in my life. One came down in the cornfield behind my house and went away from my house thankfully.

[Cynette]

Originally Posted by KenWittlief

Personally I like huge thunderstorms.

I always think I like huge thunderstorms, but recently we have had the kind that scare the bejeebers out of me! Today I saw twin lightning bolts come down, they had to be a city block apart, as straight as straight could be and on either sode of the road I was traveling on. Makes you go WOW
I'm glad I wasn't at the end of them! And I certainly wasn't going to go look for any rainbows that they left behind!
Oh no, they are starting up again, about 3 seconds from flash to sound... no matter what the calculation is, I'd better get off my computer, even with the surge protector, we've lost the router before!

[KenWittlief]

Penfield - I was just going to say, speaking of Tstorms! We got one right now here in Fairport, NY

We have made some significant improvements over the years. All I have to do is reach over and pull the charger plug on my laptop, and Im running on a 'free UPS for 3 hours', completely isolated from the grid.

No chance of getting zapped through my cellphone either!

[KathieK]

Originally Posted by skimoose

This was the lightning storm that rolled through on 7/28/06.

That was a nasty series of storms last Friday. I was surrounded by lightning on all four sides as I drove home from work (but no rain on the whole drive home until I got to my street). There was a lot of cloud-to-ground as well as cloud-to-cloud lightning. I have to drive under some high tension wires twice in my short trip home and both times I was praying that lightning would not choose to hit those as I passed underneath.

[Nica F.]

that is pretty scary. was there a lot of that around?
i havent been in a major thunderstorm in my life.

[JaneYoung]

Severe thunderstorms can be dangerous, frightening, exhilarating - and they can encourage a healthy respect for Nature quickly.

Here in Texas we get blue northers - the sky will turn a funny blue and the winds will change. Usually in the fall but it can happen any time. Usually there is a severe drop in temperature, sometimes storms.

I've lived in the same house for 20 years and lightning strikes all around us. We have huge sycamores in our neighborhood - towering trees. Lightning took the top out of our neighbor's tree a few years back and laid it across our roof and across the length of the lawn with 20 feet of the tree base still standing.