|Subject:||Re: [TowerTalk] Ground Rods|
|From:||Jim Lux <email@example.com>|
|Date:||Tue, 04 May 2004 09:49:09 -0700|
At 08:07 AM 5/4/2004 -0700, Bill Turner wrote:
On Mon, 3 May 2004 18:38:26 -0600, Grillo's wrote:
The voltage in a lightning stroke is immaterial (mostly because it's spread over many thousands of meters of air), but the current is what does the damage (or, in some cases, the di/dt, which induces a voltage in nearby conductors). The goal is to keep the voltages in your system low enough to be reasonably handled.
Figure 25kA for a typical lightning stroke.. 25kA at 5 ohms is 125V.. not enough to flash over in air and well within the transient suppressing ability of many devices.
25kA @ 300ohms is 7500V, more than enough to flashover to adjacent conductors, and well beyond most transient suppression devices.
So.. reasonably low impedance is a "good thing", although the practical difference between 5 ohms and 10 ohms isn't all that signficant.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
_______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk
|<Prev in Thread]||Current Thread||[Next in Thread>|