[BC] Lightning and grounding - tower differences matter?

[Robert Meuser]

Phil:

I have used dissipation devices very sucessfully on series fed AM towers. Over 15 years 
with no damage to any equipment in the plant. We always went on generator before a strom 
hit and there were instances where the LEA surge supressor on the power entrance 
sustained damage, but since the plant was on the generator, nothing else was affected (we 
didn't even know the LEA took a hit until an inspection several weeks later). 

I was always told that the system worked by NOT dissipating all the energy but allowing 
the tower potential to rise and thus have less differential than other objects in the 
vicinity. This may well be why this does work on towers but not other structures where 
there may be multiple discharge paths.

I do know I have have seen severe strikes near the tower but as I stated earlier not one 
piece of gear in the transmission chain ever taken out.

R



On 19 May 2005 at 10:57, Phil Alexander wrote:

> 
> I've come to the point of believing they may have value on towers, but
> I'd never use them for building protection, or anything else. I think
> Cowboy made an excellent suggestion earlier in the thread when he said
> he used charge dissipation devices and Franklin rods together on towers, 
> and IMHO that may be the best way to do it.
> 
> When they are used, Alan's point about grounding and conduction from
> ground to the device is obviously VERY important. A very low impedance
> between device and ground is essential if they are to carry significant
> "dissipation" currents. This suggest effective use may be problematic
> with series fed AM towers, and also suggests a need for extremely good,
> very low resistance bonding for grounded towers, as well as a very good
> ground termination (IOW a pattern of long rods, and possibly chemical
> augmentation).