Help me identify an "object" on a 420 kV line

[Bavuka]

Hi

I saw this 420 kV line and I am not able to figure out the meaning of the extra wire (marked with red arrow). My suggestion is that it is used to increase the tension in that particular cable, what do you think/know?

 

[.Scott]

If I had to guess, I would say that it is used during maintenance as a good place to clip onto the live wire without risking damage to the main load-bearing section.

What part of the world was this photo taken?
If it's northeast US, I can ask a local lineman.

 

[anorlunda]

I vote for @.Scott 's interpretation. It is possible that the cable was physically damaged in the sagging part, the taught part is a temporary repair.

 

[jim hardy]

Hmmm

my first impression was a home-made mechanical damper
at 400 % there's another one on a different wire

i've seen plenty of these Stockbridge dampers before

https://en.wikipedia.org/wiki/Stockbridge_damper
but were that its purpose there'd be one on each conductor.

so i'd be guessing.
My guess is it's just a piece of smaller conductor to which the utility linemen can conveniently attach their grounding clamps(or bonding clamps if working hot) when doing maintenance. .

http://www.waybuilder.net/free-ed/Resources/05 Building and Construction/Electrical/WorkingLiveLines.asp

Is there a lineman in the house ?

 

[Bavuka]

What part of the world was this photo taken?

Picture was taken in southern part of Norway.

Each phase have one wire as shown in the picture, as well as the other nearby pylons.

 

[Tracey3]

To my knowledge in some places when helicopters work on power lines, they are not allowed to hook onto the lines incase they have to pull away fast. I have seen a gif before were they weave a straight rod through what's on the picture and then rest it on the parallel line, to create leverage on the rod. My guess its just there to make the air teams life easier.

 

[Bavuka]

Thanks all. So I guess its safe to say its most likely there to make any maintenance work etc. easier/safer.
If I am able to get in touch with the local power company, I will ask them and post their answer here.

 

[jim hardy]

If I am able to get in touch with the local power company, I will ask them and post their answer here.

That's something the average office worker probably won't know. I'd suggest print the picture and stash a copy in your glovebox. Next big utility truck you see stopped for lunch someplace, ask the guys on it.

http://www.snopes.com/college/exam/barometer.asp

 

[ACF]

It is not my speciality but I may say these "things" are not for maintenance work. Transmission line is using a 3 conductors bundle an looking at the picture I can see is in the lower conductor making it difficult to reach it from air. For grounding the lines it will be also difficult to reach them from structures, and because these "things" are also present in ground wires on top, the arrange of theses makes me doubt.
I don't believe these are dampers, but they may be used as visual indicators of torsional stress. Stranded wire under tension (pulling stress) tends to turn damaging external layers of conductors. As phase in the center of picture, it seems to have turned once.
Where I live, transmissions lines are different so this is only an idea.

 

[jim hardy]

I'm close to @.Scott 's thinking.

My thought was it's likely a bit smaller than the main conductor
(can't quite see at resolution of the image)

these snap-on grounding clamps will handle cable up to 1.56 inch, 40mm which is about 1600 mcm
http://www.hubbellpowersystems.com/catalogs/lineman/3000_Grounding.pdf
if those main conductors are bigger than that the linemen will have difficulty grounding the line.

and i do find bigger wire in the catalogs
http://www.prioritywire.com/brochures/Utility Catalog.pdf

But high line work is not in my experience so it's a guess ..

I do know somebody to ask - will do...

old jim

 

[CWatters]

Darn. Now I'm going to be looking out for them on every tower I pass :-)

Edit: I think there is even one on the top left wire in the OP photo (usually earth).

 

[Bavuka]

I took another picture today, showing the top conductors also have this extra cable.

 

[Bavuka]

I uploaded the same picture in post #12 using gyazo, a picture with slightly better resolution can be found here: https://gyazo.com/33d26480ec0b88832d800e08cb0b6764

 

[anorlunda]

What do they do when a couple of strands in the cable get broken? It could get nicked by a bullet.

 

[Bavuka]

I sent an email to the company that owns the line and got the following reply (translated from norwegian):

This is a "viberation damper".

In long cables and lines, vibrations often occur due to temperature changes, weak wind and other atmospheric events. Such a "loop" or cable stump helps to dampen this vibration in the line itself.

 

[jim hardy]

Aha ! I should've read further into that Wikipedia article

https://en.wikipedia.org/wiki/Stockbridge_damper
The Stockbridge damper was invented in the 1920s by George H. Stockbridge, who was an engineer for Southern California Edison. Stockbridge obtained US patent 1675391 on 3 July 1928 for a "vibration damper".[6] His patent described three means of damping vibrations on lines: a sack of metal punchings tied to the line; a short length of cable clamped parallel to the main cable; and a short (30 in, 75 cm) cable with a concrete mass fixed at each end.[6] It would be this last device that developed into the widely used Stockbridge damper.

That could be a variation of the ones I'm accustomed to seeing, pictured in post 4Thanks Bavuka !

old jim

 

[jim hardy]

From Stockbridge's 1928 patent here:
(you might need a TIFF reader to see it at the US patent office site)
http://pdfpiw.uspto.gov/.piw?PageNu...1=1675391.PN.%26OS=PN/1675391%26RS=PN/1675391

His invention was a resilient damper.

Still seems to me strange they're only on one of the conductors in each phase, though.

old jim

 

[Bavuka]

Still seems to me strange they're only on one of the conductors in each phase, though.

I took another look at the line, and noticed that the first tower directly after the step up transformers from the power station had three dampers per phase, while the next three towers I was able to see had only one damper per phase.

 

[ACF]

Bavuka is right. I heard also that these are vibration dampers. Resonance on lines is absorbed by these.
It seems they are installed on long spans of lines crossing rivers, where wind is main reason for damage on lines.