Re: [TCML] protecting appliances

[Jim Lux <jimlux@xxxxxxxxxxxxx>]

-----Original Message-----
>From: Frank <fxrays@xxxxxxxxxx>
>Sent: Jun 5, 2008 4:20 PM
>To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
>Subject: Re: [TCML] protecting appliances
>
>
>Now, lightning rods. They are not a point for the lightning to be 
>attracted to, on the contrary, they bleed the charge into the sky to 
>discharge the potential of the clouds about the rod. 

This is incorrect. A simple calculation of the amount of charge in a typical cloud and the current flowing in the rod before a strike will show that nothing can do a lick of good in terms of "discharging the potential".. even after the lightning stroke, lots of charge remains.

Just to add a bit more.. the "porcupine" style "lightning dissipators" do not work.

More at http://home.earthlink.net/~w6rmk/lightning.htm


>it is very important to have an excellent ground, even better 
>multiple grounds with large metal sheets buried. A grounding rod will 
>not do, you need a large surface area in contact with the earth. The 
>conductor from the ground to the rod is usually 3/8" dia heavy copper 
>wire, 3/8" tubing will work too, all connections are soldered to 
>minimize resistance.

Grounds are good. Tubing is not.  High currents cause the tubing to fail structurally.


>The rod must come to a sharp point to be effective. In fact, you have 
>to do periodic "maintenance" on the rod by sharpening the point as it 
>gets dull with the continued discharge.

Numerous peer reviewed experimental and theoretical studies have shown that the shape of the "air terminal" doesn't have any real effect on lightning protection ability.


>There is specialized testing equipment to verify you have a good 
>ground first and foremost and then virtually zero resistance 
>connection from the ground to the rod. There can be a lot of current 
>flowing during a storm. Any resistance in a joint or connection, even 
>very low, can turn into a significant voltage drop during a storm.

For most lightning protection systems, inductance is a bigger deal than resistance.  The goal in lightning protection is to 
a) get the stroke current to flow somewhere other than through the structure
b) reduce to possibility of a side-flash to something else

You're going to still have to worry about transient overvoltage protection, because even a good lighting protection system will have significant voltage drops along it (especially if you take a 300kA super stroke).

There's a great book published by Dover Press for about $20 by R. B. Standler called "transient overvoltage protection" or something like that. Amazon has it.

>
>I have 2 antique German lightning testers with instructions as well 
>as numerous books on the subject.
>
>Frank
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla