BJ, some helpful information given there on the lightning strikes and ground. I beg to differ, though, on some of it, but since it's all theory anyway, I don't consider it an arguement, just another viewpoint.
Likewise, I realize my theory isn't popular, but I was introduced to it by a fellow who worked on very tall professional towers. I didn't believe at first, but the more I thought about it the more I was converted.
....... I don't follow the potential induction thing. However, the results are what counts. A "near-miss" with lightning will induce a voltage into conductors
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I don't think I explained my theory well. When I used the word induced, I wasn't referring to a coil type induction, but a capacitor like induced polarization. Ie when one side of a capacitor gets a positive charge, the other plate acquires an induced negative charge. Basically the principle that like charges repel each other. If a cloud is negatively charged, it will repel electrons in the poorly conductive surface, and the surface will be positively charged, compared to a zero volt ground potential. If a cloud is positively charged, electrons will be attracted to the surface, giving the poorly conductive surface a negative charge.
Raising a metal tower and grounding WILL attract lightning that is going to strike nearby by giving a path to ground (or from ground, in some cases).
This path to ground issue only becomes important AFTER a lightning strike begins. For a lightning strike to begin, a couple things have to happen, and again, I think I referred to voltage differential, but perhaps voltage gradient would have been better. Basically, for a lightning strike to start, what has to happen is for a voltage gradient to increase to an extent where the normally non-conductive air breaks down into sort of a plasma of ions, which becomes conductive. Once this happens, then, and only then does the path to ground become important. The thing about the voltage gradient, which is basically a volts/distance parameter, is that this becomes higher via either increasing the voltage, or decreasing the distance. With all else being equal, putting up a tower decreases the distance to the cloud, so a tower is more likely to be hit by lightning. However if you GROUND the tower, you are reducing the voltage differential by a factor of two, thus decreasing the voltage gradient, making the tower LESS likely to be hit, if it is grounded. Depending upon how tall the tower, and how low the clouds, the tower may still be more likely to be hit, but the bottom line is that the voltage differential is less for a grounded tower, so grounding a tower makes a strike less likely.
I've drawn a couple pictures in the attachment below, showing off my first grade art ability. The first picture shows tower, house, and tree with no cloud, and the poorly conductive surface at zero volts. The 2nd picture shows a positive cloud, and an ungrounded tower, house and tree. Due to the capacitor polarization effect, the surface will become negatively charged, as will the ungrounded tower, house and tree, and the strike will go to the tower.
In the third picture, again the positive cloud, and negative surface, with negative tree and house, however the tower is now grounded, so it is zero volts instead of some negative polarized voltage. In this case, since the voltage differential is twice as high between the tree and the cloud (ie 2V/D instead of V/D ), the strike will go to the tree instead of the tower.
Anyway, that's the theory, which is really a collection of a variety of theories from people many of which come to different conclusions. Where the strike occurs depends on many factors, and isn't predictable, however I'm just trying to illustrate why grounding the tower is actually a good thing towards prevention.
a very large voltage can be induced into nearby (within say 1/2 mile??) conductor as mentioned above and even metal piping, to include conduit as well as water/gas pipes. This is prevalent in hits that burn wires all the way to water pumps on farms and houses, etc.
Speaking of water pumps.... about a year ago, we had a very nearby strike here. It did take out a couple of my receivers, thanks to a poorly installed DirecTV dish. But the amazing thing is that the lightning was looking for your "path to ground", and found the pipe on my water well. The well itself is about 500' deep, but the metal pipe only goes down 30' or so into the bedrock I think. But when the lightning hit that pipe, it scoured off all the rust and other deposits on the well casing, and perhaps off the sides of the hole in the rock. I went to wash my hands a bit after the strike, and the water was a deep red-purple-brown color. Couldn't even see through a glass of the water. I ran the water for about 45 minutes, and it cleared up quickly, but that was amazing. Didn't hurt the water pump at all, it just cleaned off the pipe.
Anyway, I just wanted to explain my theory better. I realize not many if any people will be convinced, but I am.
