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#66678 - 06/14/06 09:07 AM Q's for linemen  
Mike Wescoatt  Offline
Member
Joined: Jun 2001
Posts: 161
Cedar City, Utah
1)On HV lines all over the place what are the little winged things that are attached near the insulators on the wire? On some systems I have seen oval loops instead of the wings. What are these for?
2)On some three phase systems (I am assuming delta) there are a pair of much smaller wires running above the main conductors. The three phases are under a horizontal bar on maybe 7-10 bells. The bar is supported by two wood posts and there are thin wires on the top of the posts on a single insulator. Ideas on what those are for?
3)I know I've seen a thread on it before, but I can't find it now... Are there good books or catalogs where I can learn more about HV distro systems and parts???

Thanks everyone!!


Mike Wescoatt

Work Gear for Electricians and the Trades

#66679 - 06/14/06 07:58 PM Re: Q's for linemen  
Larry Fine  Offline
Member
Joined: Feb 2005
Posts: 693
Richmond, VA
1. Those are harmonic dampers. They reduce wire breakeage at the support clamps by absorbing wind-induced wire vibrations. They're similar to the dampened weights in the ends of modern motorcycle handlebars.

2. Those are typically grounded to the towers, and are considered as static drain, lightning, or 'neutral' conductors, although HV is usually transmitted as Delta, with line-to-line transformers, no real system neutral.


Larry Fine
Fine Electric Co.
fineelectricco.com

#66680 - 06/14/06 09:19 PM Re: Q's for linemen  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Yes,
Larry is correct on 1)These are commonly known as Stockbridge dampers.
This vibration, called Aeolian vibration can gain enough momentum, if allowed to continue, to snap the line away from the insulator stack.


Let's face it, these days if you're not young, you're old - Red Green grin

#66681 - 06/14/06 09:37 PM Re: Q's for linemen  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
I have heard that the grounded bare wire at the top of the pole is there to give birds a (more desirable, higher) place to perch, and keep them off of the hot phase conductors, where they can cause outages.


#66682 - 06/15/06 09:14 AM Re: Q's for linemen  
Mike Wescoatt  Offline
Member
Joined: Jun 2001
Posts: 161
Cedar City, Utah
Cool! Thanks guys. I thought that they might have been something for corona or static something or other. I never thought about wind induced occilations...


Mike Wescoatt

#66683 - 06/15/06 12:50 PM Re: Q's for linemen  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,076
Estero,Fl,usa
On our recent driving tour of the southwest we took a hot air balloon ride in Albuquerque. It ended up being a study in power lines when the balloon pilot found out I was an electric kinda guy.
It appears the static lines are only on high voltage lines in that area. The medium voltage primaries had the grounded conductor lower on the pole with the single or 3 phase lines on top.
I showed him how to look for insulators and to look at how the lines got connected to the transformers but the reality is, if you get tangled up with any of these wires you are screwed.
It turns out these hot air balloons are really out of control most of the time and they get hung up on stuff more than you hear about. We heard a story of "Smokey Bear" who hung a balloon on a 1500' radio tower that everyone had to climb down. (that now "bears" his name) We ended up landing in some guy's back yard. The shreaded dog toys were somewhat alarming but he said the dogs were in the house.

I guess that is why "trespassing arrest" is one of the things you waive the right to sue him for in the release.
Of course the main thing you waive is "flaming crash" from a power line strike.


Greg Fretwell

#66684 - 06/18/06 07:25 PM Re: Q's for linemen  
subtech  Offline
Junior Member
Joined: May 2006
Posts: 5
Kansas City, Missouri, USA
1. As others have mentioned, the "winged" things are most likely vibration dampeners.
2. Those "hoops" or oval things are more than likely on lines whose voltage phase to phase is 230KV or higher and linemen typically refer to them as corona rings. At voltages from 230 and up, it is very common for the little electrons to want to jump from any sharp edge or from hardware out into the clear blue sky.(corona discharge) That in itself wouldn't be so bad, except for the fact that when they jump, they take small bits of conductor or hardware with them. This eventually leads to equipment/conductor failure and is very undesirable.
#3
Those "thin wires" at the top of the structure that are above the main conductors are generally called static or sheild wires. They are usually tied to earth ground at every structure and their main purpose is to provide (hopefully) a convenient path to discharge the energy from a lightning strike. I say hopefully because if the lightning hits the static or shield wire and it is effectively grounded, it will not proceed further and strike the phase conductors as well quite possibly causing an outage or line damage.

#4
Handy books to have around are the Linemans and Cablemans Handbook, and "Electrical Essentials" which was written by Wayne VanSoelen and Published By Delmar/Thomson Learning.
A search on Amazon.com in the used book section may line you up with some bargains on either or both of these.


It is better to be thought of as a fool, than to open ones mouth and remove all doubt.


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