I'm going to stick my neck out here and say from two
experiences with this topic, there's a couple of things
to consider ...
First, ideally, any potential difference between GROUNDS
should be zero. If you had asked about NEUTRALS, I'd have
to say - unknown. The physical connection is a function
of the connection to the transformer by the electricians
and imperfections in the transformer.
Second, it's a function of what's sourcing the difference.
I worked at a place where the outlets in one half of the
lab were supplied by a different substation than the outlets
at the other end of the lab.
Without knowing the issue, we connected two different machines
with a coax. Each machine eventually connected to different
substations by way of differently sourced outlets. And we
watched with amazement as the rubber jacket of the coax melted.
All with a 15V difference. The electricians were notified
and the problem was solved but a potential difference of
some sort was still there. I don't think you'll ever get
away from it.
So, I guess what I'm saying is that you should not only
consider the voltage difference, but the power involved.
And that would be have to tested some other way.
- Doug McKean
Kelly Tsudama wrote:
>
> Hi gang!
>
> I have been asked to look into ground potential differences by one of the
> teams that I support. Can any of you provide any insight on how I can
> determine the maximum potential difference between different ground circuits
> within a building??? I've heard numbers ranging from 2V to 50V!!! Even with
> all the bonding requirements in the NEC, there must be some voltage
> differential between grounding points???
>
> Thanks for any help you can provide.
>
> Kelly
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