Electrically correct 2

[PPC800]

Good Day,

Is it electrically correct (in terms of wiring standards) to use the shield wire in a cable as Ground(-).

 

[waross]

No. Using the shield drain as a ground may result in currents flowing in the shield. Thus the shield may radiate part of the energy that it was intended to suppress.
There may be issues with ampacity and voltage drop in the event of a ground fault.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[RRaghunath]

Shield wire can help shield the flux from the power cables from leaking out and linking with the nearby metallic (magnetic) structures / pipes etc., when the shield is earthed at both ends of the cable.
In case of single core power cables, it is also a practice to earth the shield wire only at one end to avoid derating the cable while sizing.
Shield wire, in either of the above cases, may help clear the cable phase-to-earth fault faster but that is only incidental.
The shield wire is not considered in the Earth grid sizing calculations.

 

[itsmoked]

You power heads!

Yeah, but if he's talking RS-232 - give it a shot. It's done all the time.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

The question was 'is it correct', not do you light-current clowns do it all the time and get away with it!


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If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

What works reliably is 'correct' in Commland.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

LOL, when I was in High School, my world was divided into cliques of Jocks, Nerds and Stoners, and I had trouble deciding which group I fit in to at any given time. Now I have to decide if I'm a "Power Head" or I live in "Commland", but PLEASE tell me there is at least a 3rd alternative! Maybe "Control Freaks" since we tend to use elements of both of the other two groups?


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[MacGyverS2000]

I mostly write firmware, but I'm not so sure I want to be called a "Firm Head"...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[geekEE]

In audio, the shield is used as ground in unbalanced and balanced audio cables. Both are "standard." And yet unbalanced audio cables can create the most horrendous hum in the audio because of circulating currents. Just because something is standard doesn't mean that it's good.

Hmm...is someone in audio an "aud head"?

Glenn

 

[ScottyUK]

In industrial instrumentation the shield is frequently earthed at the quiet end and left floating at the noisy end to avoid earth loops.

And don't even think about calling me a Tiffy!


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If we learn from our mistakes I'm getting a great education!