Re: [TCML] top load and photography (tripod grounding)

[bartb <bartb@xxxxxxxxxxxxxxxx>]

Hi Phil,

>  
>     But it's implied that after Peter grounded the  tripod, the "tingle" went 
> away. This would mean that the camera was originally  not at ground 
> potential, but Peter's body was.
>   
Likely neither was at ground potential, but the potential difference 
between Peter and the camera was lowered when the tripod was grounded. 
No problem with that. The tingle was simply an indication of a potential 
difference (several thousand volts).
>  
>     The same theory that "standard" safety grounding  is based on applies 
> here as well. If a conductive object is in contact  with your body, if it's 
> grounded then the current should take the path of the grounding conductor instead 
> of your body. 
>   
Of course it should, but that isn't the issue.
>  
>   
> I don't think being in bare feet would make much  difference WRT strikes from 
> the topload. But it might save your life if you  get in contact with anything 
> on the primary side (or the line side!). Besides,  you might step on 
> something painful which causes you to jump or fall into live  equipment.
>     Who does this stuff in bare feet, anyhow? 
>   
Just an analogy of grounding your body (bare feet is a good way to do 
it). Standing in water, hooking up your body to a grounded conductor, 
whatever.
>     
>   
>     That's a valid point, but I bet even if the tripod  wasn't intentionally 
> grounded you'd still be in bad shape if you took that strike. I don't think a 
> ground wire to the camera would make much difference.
>   
It certainly could make a difference. Ever notice how bright those 
steamers get when they contact ground?
>     If I was out in the middle of a field holding a lightning rod, I'd 
> really prefer to have the lightning rod solidly grounded, not  free floating in my 
> hands. Almost a moot point? Better to stay out of a bad  situation!
>   
Ok. After the lightning rod is solidly grounded, and you grabbed it in 
one hand (camera click) and got jolted on your other hand? Now what? 
Could it be that because the rod was grounded so were you, and you 
became a nice target? Yes...
>     FWIW, I remember when I was running my 4" coil in  the garage, and the 
> thing reached out with a 4' strike to a big  polyethylene trash barrel. One 
> strike only! Apparently it was attracted to the  static surface charge on the 
> barrel. Once it "sucked all the charge" off the  barrel with a hot strike, it 
> never tried to hit it again. So even if  you're conscientiously wearing 
> well-insulated footwear and  staying away from grounded objects, you might still make a 
> highly attractive target to a strike.
>   
Could happen. Again, stay out of harms way.

Grounded targets are obvious, but that is only one aspect. There are 
also hv transients that ride on ground.

Take care,
Bart

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