Power line videos. Neat stuff

Do a search on Jacobs Ladder Arcs.

| 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).

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

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

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

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

Think before you speak, boy.

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.

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.

On Wed, 16 May 2007 02:49:32 -0700 The Great Attractor wrote: | On 15 May 2007 12:31:24 GMT, snipped-for-privacy@ipal.net wrote: | |>On Tue, 15 May 2007 01:31:32 GMT JohnR66 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.

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

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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.

--------------- 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.

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

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

Nice guess though.

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?

Another horizontal Jacob's Ladder of sorts.

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 snipped-for-privacy@shawcross.ca remove the X to answer

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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.