curious loops of wire on HV transmission pylons

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I was being chauffered around Illinois this weekend, and was able to get a  
better look at something I've seen while driving.  Now, I figured out a bit
more of what I was looking at.

So, on HV transmission lines, they have 3 (or 6, if it is a double feeder)
phase wires, and typically 2 shield wires on top.  Generally, the shield  
wires are grounded at each pylon.  Well, I noticed that every mile or so,  
there is a loop of wire mounted flat to the pole.  Now, while not being the  
driver, I was able to see that the shield wire is interrupted and the loop
is in series with the shield wire.  Driving along the same feeder for a  
while, I was also able to see that the loops always seemed to be on the same  
shieled wire, they did not alternate from one wire to the other.

These loops appeared to be about 2-3 feet in diameter and consist of a  
number of turns, with a silvery round object in the center.  It was not  
clear at a distance, but the wires may NOT have been insulated, they  
appeared to be a silver color.

So, I have been wondering what these are.  Are these to add inductance to  
the shield wires, so as to not add a shorted turn to what is, in effect, a  
huge air-core transformer?  But, doesn't grounding the shield wire at each  
pylon defeat that?  Or, is the resistance of the earth so much greater than  
the wire resistance that it doesn't matter?

Or, is this to prevent shorting out the power line data transmission  
signals?

Anybody know?

Thanks,

Jon

Re: curious loops of wire on HV transmission pylons
On 14.5.18 19:14, Jon Elson wrote:
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Are you sure that the loops you see are not fiber cable?

There are often communication fibers along with the ground
wires at top.

--  

-TV


Re: curious loops of wire on HV transmission pylons

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Indeed, there is a cable product that is BOTH. Not something I use, but  
something that I'm aware of. Those cables have to be there anyway, the  
right-of-way is already there, so the minor cost differential to add  
fibers is exactly that. Not useful or economical in my plant, but then,  
I don't have any HV transmission lines...

https://en.wikipedia.org/wiki/Optical_ground_wire

--  
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

Re: curious loops of wire on HV transmission pylons
On Monday, May 14, 2018 at 12:15:01 PM UTC-4, Jon Elson wrote:
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This took 5 seconds to find:
"It is necessary to have constantly
operational monitoring systems which uses electric
powered devices for transmission of electricity over high
voltage transmission lines. This paper investigates a
source of power to feed these ancillary service loads since
the conventional power supply systems are infeasible. The
voltage induced in the shield wires of an HV transmission
line is tapped off, regulated and used as a power source.
We use a dc-dc converter inorder to get a regulated dc
output. The results obtained shows a feasible and cost
effective alternative for power source."

Re: curious loops of wire on HV transmission pylons
On Mon, 14 May 2018 10:17:17 -0700, bloggs.fredbloggs.fred wrote:


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Your google-fu is much better than mine!

Quoted text here. Click to load it

Thanks, that also explains the silver boxes in the center of the coils.
But, actually, why do they need the coils?

Thanks,

Jon

Re: curious loops of wire on HV transmission pylons
On Monday, May 14, 2018 at 3:12:07 PM UTC-4, Jon Elson wrote:
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Sounds like it may an air-core transformer method of coupling discussed here: https://core.ac.uk/download/pdf/54204183.pdf

Re: curious loops of wire on HV transmission pylons
On Monday, 14 May 2018 20:12:07 UTC+1, Jon Elson  wrote:
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voltage on an earthed conductor is minimal. A transformer solves that & can protect from shorts to live.


NT

Re: curious loops of wire on HV transmission pylons
snipped-for-privacy@gmail.com wrote:
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Several months ago I asked if something like that could be used to power  
logic in appliances.  I guess it is feasible then.




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