[c-nsp] Galvanic isolation for Ethernet?

[Victor Sudakov]

Michael Loftis wrote:

[dd]

> >> The root cause is almost always bad grounding in one building or
> >> another.  In a couple cases we discovered that ants and termites had
> >> colonized around the grounding rod.  In another we discovered the
> >
> > Our electricians say that the grounding is correct, all grounding
> > circuits on the site are interconnected and that they measure the
> > parameters annually.  I am not the person to expose them to be lying
> > (if they really are), I lack such qualification.
> 
> Have you checked to see how much potential difference is at one end or
> the other?  

Yes, I have just had it checked at my request.

> (Disconnect equipment from one end, and measure voltage
> between the various RJ45 pins and ground, should be 0.00) 

We have checked between the switch ground and the RJ45 pins of the
disconnected incoming cables, it's zero.

> And how much
> current is flowing? (set meter in mA and do same)  

Zero.

> Worse your issue
> could be entirely intermittent too.  Yes, you're dealing with
> gremlins.  Just because the individual buildings are OK doesn't mean
> they're OK with respect to eachother.  You can have grounding
> potential differences in different floors of the same building or
> different areas of the same building.
> 
> And all of this is assuming it's grounding potential
> differences....not something like your bundle of Cat5 runs right by a
> big industrial refrigerator, or a sodium light or something like that
> which is inductively coupling to your Cat5 run.

There is some industrial equipment in the vicinity. That's why we had
installed Ethernet protection (which proved ineffective this time).

-- 
Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
sip:sudakov at sibptus.tomsk.ru