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Power line videos. Neat stuff

Discussion in 'Electrical Engineering' started by JohnR66, May 15, 2007.

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  1. JohnR66

    JohnR66 Guest

    Confetti causes a flash over between power line conductors. I wonder why it
    travels horizontally like that?


    I thought this one was pretty neat. A linesman servicing HV lines from a
    chopper.
     
  2. Do a search on Jacobs Ladder Arcs.
     
  3. Guest

    | Confetti causes a flash over between power line conductors. I wonder why it
    | travels horizontally like that?
    |
    |
    | I thought this one was pretty neat. A linesman servicing HV lines from a
    | chopper.
    |

    Do you have normal videos for these? YouTube still can't figure out what
    version of Flash player my browser has (likely because their code does not
    understand Linux).
     
  4. JohnR66

    JohnR66 Guest

    Heat seems to pull the arc up, but this is horizontal and judging by the
    sparks there is little or no wind.
    John
     
  5. John Rye

    John Rye Guest

    Hello All

    I have not seen the video, but if you have a pair of parallel wires, and
    establish an arc between them it will travel along the wires away from the
    power source. Remembering that the arc could be replaced by a piece of wire,
    if you work out the force on the piece of wire, by doing the appropriate
    integrations on the fundamental equation Force = Flux Density x Current x
    Length you will find that with a few thousand amperes of current there is a
    significant force in this direction.

    There is a message in this for those investigating equipment failures. That
    is that the major damage will be where the arc ends up. The place where the
    failure started is usually somewhere back towards the supply from this point.
    You can usually find a series of bright spots on the conductor where the arc
    was stationary for a few milliseconds.

    If you consider single phase ac supplies the arc will often go out for a
    short time at current zero and then restrike.

    John
     
  6. Some local lines have coatings on them, and the burn travels along as
    the coating is breeched.
     

  7. Totally incorrect. Such arcs operate on the rise of heat in air. This
    was HORIZONTAL.

    Think before you speak, boy.
     

  8. What I hate is all these damned sites that allow one to view, but not
    save a clip.

    They act like they are going to lose money or some such SPAM related
    CRAP.
     
  9. Pretty silly. Arcs find least resistance paths, period. Air ionizes
    around them, and some lines are coated, so an arc could move in either
    direction.

    These were parallel lines, so it likely moved along them as it breeched
    the coating on them, blazing a trail as it were.
    Any arc that remains stationary is going to heat up the start and
    finish points (which each is both for AC) heavily at the location where
    it stands in one place.
    Since all three phases are not carried on ONE pair of lines, the same
    occurs one a three phase system where the arc is typically only on one of
    the phases.
     
  10. Guest

    | On 15 May 2007 12:31:24 GMT, wrote:
    |
    |>
    |>| Confetti causes a flash over between power line conductors. I wonder why it
    |>| travels horizontally like that?
    |>|
    |>|
    |>| I thought this one was pretty neat. A linesman servicing HV lines from a
    |>| chopper.
    |>|
    |>
    |>Do you have normal videos for these? YouTube still can't figure out what
    |>version of Flash player my browser has (likely because their code does not
    |>understand Linux).
    |
    |
    | What I hate is all these damned sites that allow one to view, but not
    | save a clip.
    |
    | They act like they are going to lose money or some such SPAM related
    | CRAP.

    If you can view it, you can save it. You just have to be using software
    that obeys the user, or something sniffing the video card buffers. BTW,
    features in the new Vista from Microsoft intentonally try to prevent that.

    I would not mind watching the video directly from YouTube, if they would
    make it work universally. But that probably means they would ose certain
    abilities to control other people.
     
  11. John Rye

    John Rye Guest

    Hello

    Agreed that arcs normally find the least resistance path.

    Agreed that if the conductors are insulated it will slow the movemant down.

    But you are forgeting the magnetic forces. The arc will move away from the
    power source, and I have plenty of videos from experiments demonstrating
    this. Unfortunately they are on film, and can not therefore easily be put on
    the web.
    Sorry but no. The arc will run on all 3 phases. If you look at a high speed
    film you can see the current zeros occuring on each phase, but except for
    these very short breaks, on a three conductor arrangement with bare
    conductors there will be arcs on all three conductors.

    John
     
  12. Don Kelly

    Don Kelly Guest

    ----------------------------
    "The Great Attractor"
    --------------

    There is a short between lines - current flows- magnetic force is present
    and tends to expand the loop and this alone can cause movement of the arc
    (and is also a major factor in Jacob's Ladders-more so than thermal
    effects).
    This arc had little upward expansion so heating wasn't the source. A
    horizontal Jacobs ladder should work.
    Fats, you should be able to try this.
     
  13. Don Kelly

    Don Kelly Guest

    ----------------------------
    ---------------
    Actually the most common arcing fault on a 3 phase system is line to ground
    on one phase. However, it can, if not cleared become 2 line to ground and
    then involve all 3 phases.
    In many cases single pole clearing and reclosure works well.
    --

    Don Kelly
    remove the X to answer

    ---
     

  14. Try "Devil Ducky" and hunt up the same clip.

    http://www.devilducky.com/all/
     

  15. Look again. THAT WAS a three phase line, but only two lines were
    arcing.

    Nice guess though.
     

  16. I have had jacob's ladders where the arc sits at the bottom without
    moving up the conductor pair at all.

    The thing needed adjustment, and the ACTION was effected by THERMAL
    energy carrying the arc up the non parallel conductor pair. Since the
    top is wide, when the arc finally quenched, a new arc forms at the bottom
    (least resistance path), and the process starts again.

    It is 100% thermal in air, with the ONLY exception being in a vacuum
    vessel. Then, I would suspect that there is STILL some air in there.

    Are there DC Jacob's ladders?
     
  17. Don Kelly

    Don Kelly Guest

    "The Great Attractor"
    Of course, in a Jacob's ladder, the current is small-typically the supply
    is a Neon transformer. In a power line arc, the current will be much higher
    and magnetic forces will be appreciable (it doesn't actually take much force
    to move the arc). Have you heard of magnetic blowout on LV breakers? Sure a
    Jacob's ladder is vertical a) get a little boost from thermal forces. b)
    takes up less floor space leaving more room for spectators. c) Thermal
    effects help clear the arc at the end (the arc collapses at current 0 so air
    movement can break up the arc path).

    Yes, I've seen Jacobs ladders for which the arc didn't move. So?

    As for a DC Jacob's Ladder- definitely and with a more spectacular effect
    such as the arc reaching the end and stretching much further than an AC arc
    (at the same current) before going out. Not sure that I would want one.--

    Don Kelly
    remove the X to answer
    ----------------------------
     
  18. That's true. There are some nice extensions for Firefox web broser that
    allows you to easily download videos from many sites, including YouTube.
    Use Firefox web browser with VideoDownloader plug-in and you can download
    videos easily. Get fre FLV player application and you can play easily
    those downloaded flash videos.
     
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