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Shields and ground

This current can really be quite large, several Amperes or even tens of Amperes if TN-C

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wiring convention is used, in which part of the neutral current of an unbalanced load (or harmonics even from a balanced load) flows through the signal cable shield.

If an R or RC network is used to ground the other end of the shield, typically a 100 ohm resistor with at least a few watts of power handling capacity is used. With a 10 Vrms potential difference (caused by unbalanced 3 phase load or 3rd harmonics from rectifier loads) will dissipate 1 W in the 100 ohm resistor.

Reply to
upsidedown
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I did a little audio system for our city council chamber a few years ago, and it seemed to be fine. Then, they had the first meeting, and there was all kinds of noise. The problem? They broadcast their meeting over the local cable system. When the guy who does the cameras came in, he hooked my audio feed to his equipment, which was also connected to the cable company's equipment. MASSIVE ground noise! I had to find some ground loop interrupters and put them into my audio feed before the next meeting.

Charlie

Reply to
Charlie E.

I should have mentioned abandoning the facility as another technique for fixing ground loop problems.

John

Reply to
John Larkin

"If it absolutely, positively has to be gone by tomorrow 10:00am, call the Marines" or something like that? I bet they can make a ground loop problem go away a well, except you may need a new building :-)

--
Regards, Joerg

http://www.analogconsultants.com/
Reply to
Joerg

I recall a communications facility grounding handbook which had complete instructions for quick installation of ground rods by making the holes with shaped charges, so the Marines could have a solution not requiring a new building :-).

Reply to
Glen Walpert

Judging by your expertise in the Kablouie business, I should have thought you could do it all by yourself :-)

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)
Reply to
Fred Abse

Well, I have served, so ... :-)

--
Regards, Joerg

http://www.analogconsultants.com/
Reply to
Joerg

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