[SI-LIST] True ground versus local ground ...

Obscure interesting topic.  
Did my master's on lightning. 

Few places have "true ground". 
I've been in a couple places that have had it. 

True ground only occurs when you drill into the water table. 
For lightning rods to work the way they're supposed to, 
the rod (or it's cable) has to penetrate the local water table. 

One place I was in had the ground rod drilled into the 
earth about 350 ft.  The rod was connected to a square 
grid of pure copper cable 00, IIRC.  That was called 
a "pristine" ground system. 

The Statue of Liberty is another construction which has 
true ground.  It's ground rod goes down, I believe, 
about 300 feet.  

Local ground can be the ground grid of a building. 
Or however you wish to define it.  If you're talking 
in terms of say the power grid for California, 
"local ground" can take on several meanings. 

Same thing with products.  Just depends on how 
you wish to define it.  You can define "true ground" 
as primary ground from the mains, then any branched 
grounding can be considered "local". 

- Doug McKean 


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