W7CE wrote:
>> I'm not a student of Ufer grounds. However, I HAVE engineered some
>> large towers...including a 500' self supporter. Everyting I've
>> read says...provide a low impedance path AROUND the foundation,
>> not through it.
>>
>> Think about it...1 million amperes is going to vaporize just about
>> anything you put down there. I've seen 8" copper strap, 1/16" thick
>> simply dissapear. If it's inside the concrete, the expanding vapor
>> will cause cracking and structural failure.
>>
>> My sense of the Ufer ground was that it was intended to reduce
>> corrosive currents, and improve conductivity, not to handle peak
>> lightning strikes. Perhaps I'm wrong. I'm sure the assembled
>> expertise here can correct me.
>>
>
> I'm certainly no expert either. That's why I'm asking the questions. My
> research pointed to Ufer grounds for towers as a good solution. Ufer
> proponets claim that exploding concrete is a myth. I got the impression
> that most modern communication facilities use Ufer grounds for lightning
> protection.
>
> I am curious about something. If lightning will vaporize an 8" x 1/16"
> strap, why even bother? That tells me that #2 solid copper wire should
> vaporize in direct strike also, yet direct hits happen all the time and the
> wire and equipment survive.
>
> Regardless of which grounding system I use, I am thinking that deeper is
> better, especially since my soil is very dry for the first 7-8 feet. Here's
> an interesting link that I found last night on the subject of ground rod
> depth:
The advantage of the Ufer ground is that it makes your ground electrode
very large in surface area. Therefore it has low inductance (good for
impulses), large C to the surrounding earth (good for impulses), and low
R (good for everything).
Except in some weird cases, I would think that the tens of square feet
of surface area in even a small concrete encased electrode will beat a
single rod of any depth.
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|