[BC] Lightning

[Bruce Doerle]

>>> thebeaver32 at hotmail.com 05/24/05 12:02 PM >>>

>First, I never said that I would install one of the lightning suppression 
>systems INSTEAD of good lightning protection design.

Jerry, that is good, but it sure seemed that way and seemed like you endorsed the technology.

> I may not have clarified that point, however....it's just as important to have good 
>grounding whether you have the lightning suppression system or not.

Grounding is the absolute key to lightning protection.  You need for the lightning to dissipate through to the ground around your equipment.  However, it will not stop GRP (ground rise potential); there is were the surge protection comes into play. 

>Second, I really fail to understand why, even with a good and effective 
>grounding system, you would not want to avoid as many lightning strikes as 
>possible.

I don't think "prevention" systems are truely compatible with protections systems.  How can you have one system trying to effectively prevent a strike while another system is trying to collect/direct and dissipate the energy.  If you rely on a prevention system, you may put other components on the tower into path of the discharge.  I would certainly not want my antenna to be struck while a strike to a blunt lightning rod will not damage any of the systems.  If the antenna which is only about 10' below the top of the tower is made of brass and is pressurized.  A lightning strike on the antenna would cause serious problems.  Image a puncture in the pressurization.  BTW, when I was working for VOA in Kuwait, I was on home leave to return finding that the TX was down because of a hole in the 3300' transmission line.  This line was elevated about 4' off the desert floor stretching between a seven tower array and the TX building.  The contractor and staff though it had been hit by a shotgun pellet.  My magnifying glass on Swiss Army Explorer knife quickly resolved the problem to lightning by looking at the way the aluminum jacket blew outward instead of inward.  The jacket melted under the strike and there was a clear outward impression.  It would be quite expensive to correct a similar problem on top of the tower.

>It's my understanding that every lightning strike degrades your 
>grounding system and protective devices, even if only by a tiny bit; but 
>over time, that damage is cumulative. So, if you have the money to spend, 
>why not try to eliminate the lightning strikes?

Surge protectors certainly have their limited life especialliy if they are MOV based devices.  Our surge protector has tripped only once in two years so I am not sure that it has degraded much.  Moreover, I don't think the ground system has the same problem unless you skimped on the design.  We used 4" 19 gauge copper strap.  Periodic ground resistivity measurements will confirm the effectiveness of the system over time.

I am glad I got your attention and with many regards,

Bruce

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