[harryc]

This looks like a grounding cable - only some of the columns had these.

Are they really for grounding ? Why only a few ?

http://lh3.google.com/harry.r.carmichael/RzZKgbLXgkI/AAAAAAAAM8w/CS3nY1h5SS8/P1110592.JPG?imgmax=800

http://lh5.google.com/harry.r.carmichael/RzZKh7LXglI/AAAAAAAAM88/7ddr7w8BbAQ/P1110596.JPG?imgmax=800

http://lh4.google.com/harry.r.carmichael/RzZKjrLXgmI/AAAAAAAAM9I/8VFfsID3lT0/P1110598.JPG?imgmax=800

General site - 251 N State, Chicago - That is an electrical substation next door.

http://lh3.google.com/harry.r.carmichael/RzZKSbLXgjI/AAAAAAAAM8k/J8VcFhMkmIE/P1110587.JPG?imgmax=800

[Kelvin]

I would guess that they are running the ground cable within the column and eventually will terminate at an embedded plate or some such higher up. It has usually been my experience that the cable remains sheathed in its green insulation and not left bare.

The exact number and placement of the cables is the work of the building's EE. Given that there is a substation next door, presumably they wish to ward off stray currents and/or for a lightning rod.

[myshtern]

That is a very thick cable, they probably don't need more than a few to safely ground the entire building

[harryc]

Grounding in this building as well --- nowhere near a power station.

http://lh4.google.com/harry.r.carmichael/R098eaJbz3I/AAAAAAAAPLo/LSwikNFWtpM/P1140087.JPG?imgmax=800

[Kelvin]

Other reasons to provide grounding include lightning rods, backup generators in the building, underground trains, etc.

If there is the potential for large flows of electricity (excuse the pun), then a ground cable will likely be implemented to draw it off should it decide to flow the wrong way.

[harryc]

April 04
http://lh3.google.com/harry.r.carmichael/R_jNAJXSvBI/AAAAAAAAgtA/s5wzeihDpE0/P1290179.JPG.jpg?imgmax=800

http://lh6.google.com/harry.r.carmichael/R_jNB5XSvCI/AAAAAAAAgtM/MH1lnZzjuYQ/P1290181.JPG.jpg?imgmax=800

[aic4ever]

It's typically for lightning protection more than anything, though the electrical service must also be grounded to the building in places. This type of grounding is usually just attaching a ground wire to a column or a plumbing line.

Something like that big cable going to the rebar in the column or to the steel sheeted wall is likely part of a lightning protection system, which is a code requirement in the City for buildings of a certain size which I cannot specifically remember at this time. The connections will have to be made to a minimum number of points designed by the EE.

[harryc]

161 W Kinzie - Dec 26
Well grounded.
http://lh3.ggpht.com/_8TC_VUmf9Fw/SVaJE-4d2QI/AAAAAAABBBI/FuTBRZG6BUU/s800/P1190192.JPG

[Jibba]

^That's very interesting. As Kevin mentioned above, he has usually seen those cables sheathed in a green coating, which is presumably the insulation. Is the idea for cables like the one above that the concrete of the column provides the insulation for the ground?

[theWatusi]

well concrete does not conduct electricity, right?

no need for wire insulation

[Jibba]

^That's definitely what I was thinking, but I was just thinking that it was interesting that someone commented that they had never seen a bare wire before in this application. Seems kind of old-school to just leave it in the concrete as-is. Undoubtedly effective, though, I'm sure.

[1ajs]

a ground cable like this is run to ground the building its self if its got a jacket on it then its part of the buildings power grid but the ones pictured here are just for bonding the building its self

is an electrician

[jking]

What you are looking at, is a provision for downleads for the Lightning Protection System. Its a specially constructed braided cable available in copper or aluminum. The cable is connected to ground rods in earth near the foundation/pile cap...whatever, and will continue up the column as the structure progresses either bare or sleeved in PVC conduit, eventually penetratiing the roof to horizontal cables that connect to lightning rods adhered to roof and other metal equipment (HVAC). Its usually let by a performance specification, to a specialty contractor, under the electrical contractor.

[harryc]

Jan 12 - 161 W Kinzie, Chicago

http://lh3.ggpht.com/_8TC_VUmf9Fw/SW4z43bVdyI/AAAAAAABCiA/Xc24MwI5uK0/s720/P1200572.JPG