The best information provided here is the tail end of the Mike Holt link on the NEC 810
grounding information. The other 3 links have useful information, with again the best
is in the third link.
There was one statement given by Ron in his articles that bothers me. He states to bury
the ground wires only at a shallow depth. I would take offense to this as it is contrary
to a number of sources including the NEC articles. The NEC states to place the wires
at a depth of 30 inches or below the frost line if it greater. The reason for this is the
step potential that can develop from a buried wire. You see and hear all the time to
not stand under a tree in an electrical storm. If the tree gets struck, it will have a high
voltage induced into to the soil. As you get further away from the tree, this voltage is
reduced. This is called the step potential.
If you dig far enough into lightning strikes, you will find articles on how some cows in
a field were killed and some cows survived a strike to a tree they were around. What
has been found is that the cows that were facing away or toward the tree were killed.
The cows that were facing at right angles to the tree survived. What the research
has found was the cows that were facing towards or away from the tree, had their feet
spaced further apart to get a higher step voltage induced into their bodies. The ones
that were facing at a right angle to the tree had their feet at the same step potential
and survived.
Bottom line is to place the ground wire at a depth to reduce the step potential to
people that may be walking in the vicinity of the ground wire and a strike on the
protected structure takes place. This is also why in the NEC that it states to
ground both metal fence posts on both sides of a gate. To also run two ground
wires parallel to the fence gate opening between the post and have them spaced
about 18 inches away from both sides of the fence. This way the soil where you
stand to open the gate will be at the same potential as the gate and fence.
Tying the tower, antenna support or what ever you want to call it to the electrical
ground of the power service entrance is also trying to place both of these items
at the same potential. It is all about personal safety and electricity.
Having spent the last 15 years building cellular communication sites, you get a good
understanding for a grounding system. No one item by itself will do the job. It
takes putting all the items together to provide a good protection. This means
tying the electrical power, the telephone cables, the antenna cables, the tower,
the antenna cable ice bridge or cable tray, the shelter and the fence around it
all together in a commonly bonded system. Surge protectors on the electrical
power, telephone cables and the antenna cables are all part of this system.
If done correctly, you should be able to take a direct hit on the tower and your
communications system will stay playing. I have seen this happen a number
of times where a tower took a direct hit from lightning while I was there.
The tower steams a little in the rain, but the cell calls still keep connected.
Jim
Ok guys I did a quick search and found three links I felt a need to share, I will just post them here, as far as further technical, data don't ask me I am not anywhere near an expert on the subject.
http://www.sgcworld.com/Publications/Articles/lightning1.pdf
http://sgcworld.com/Publications/Articles/lightning2.pdf
http://sgcworld.com/Publications/Articles/lightning3.pdf
I have also seen reference to National Electric Code (NEC) 810
One more link, I linked this from mikeholt.com
http://www.mikeholt.com/newsletters.php?action=display&letterID=220
scroll down the page and click the link that says click here, or the image of article 810.
I also encourage interested people to take a look at
http://www.polyphaser.com
and see if they offer downloadable data concerning this subject.
I have done this much the rest is up to you. Please post anything you find here.
to the moderators, I haven't found a sticky or wiki on this subject...yet perhaps one should be made. If there is a sticky wiki, (sorry) let me know.
73 Ryan