Skin Effect in Solid/Stranded/Litzendraht Wire -Guy Macon

Tom Bruhns snipped-for-privacy@msn.com posted to sci.electronics.design:

Try "ACSR" (aluminum conductor, steel reinforced). There is a whole series of standard sizes named after birds.

Yes - that's two different ways of saying the exact same thing.

Probably not - a DC magnetic field doesn't generate any back EMF.

OK, go ahead and do the measurements, and post your results.

Thanks! Rich

No, it was 60Hz ac, 115kV. I know because they asked us if we'd be affected by the radiated magnetic field, being only 100-feet away from our labs, and they and we undertook an analysis, which showed we were OK about it. (I had suggested they twist the "wires" but that didn't go over well, they didn't want to twist four conduits.)

If they were in heavy lead jackets, it is very likely that there would have been no radiated EMI even a few feet away.

More like twisted brains.

Show us one, then, along with the detailed theory of operation.

Otherwise, shut up and go away.

Thanks, Rich

When I was much younger and stupider, a friend and I climbed one of those hi-line towers, and could actually reach out and touch some of the wires (luckily, they were insulated!). I actually felt the 60 Hz electrical field around the wire, which was about 1" in diameter. I don't know what the voltage was, but it was very exciting. (no pun intended.)

Cheers! Rich

No that's wrong: neither the lead nor any other shield would help to reduce the 60Hz magnetic field strength, which comes from the magnitude of the ac current, and the separation (and lack of twist) of the cables. As it happened, we found the strength of the field in our labs was a bit weaker than from our own poorly-done electrical-conduit wiring. Which we had already dealt with in sensitive experiments.

No that's wrong: neither the lead nor any other shield would help to reduce the 60Hz magnetic field strength, which comes from the magnitude of the ac current, and the separation (and lack of twist) of the cables. As it happened, we found the strength of the field in our labs was a bit weaker than from our own poorly-done electrical-conduit wiring. Which we had already dealt with in sensitive experiments.

I'm doing wiring this week (a new employee kitchen/lunchroom) so I got a little RatShack amplifier/speaker box and wired a Renco drum-core inductor to it, as a mag field probe, to trace wiring. It's really fun to wave around other things, like monitors and keyboards and such. An iPod starting up makes very strange sounds.

As I walk around, I get various 60 Hz things with no obvious source.

John

Because early TVs often had the CRT proper (and its power supply?) separate from the tuner?

We were talking about CRTs. ALL CRTs.

It has a single 0.21" copper wire in the center. There are five triangular segments or bunches around this, and each one has about fifty-six 0.1" dia (#10) copper strands. The segment orientation is not the same on the two ends of my piece, so they must rotate around the center, along the length of the cable. The overall copper diameter varies from 1.9 to 1.95 inches. The insulation layer is from 0.8 to 0.85 inches thick, and I have to assume it has no pinholes. :-)

One of the issues in the design of high voltage systems, especially AC high voltage systems, is voids. If the field strength is great enough and void large enough, you'll get corona in the void, and the very reactive ions in the corona will eat away at pretty much any organic insulation. I'd guess that not only are there no pinholes, but that they worked pretty hard to avoid voids internal to the insulation too.

Thanks for posting the details, Win.

Cheers, Tom

I should take a picture and post it on the net. At the time of the installation I did a search for information about Pirelli HV cable - datasheets, web page, anything. At the time I couldn't even find evidence that Pirelli made HV cable, let alone any detail. In a recent search I found mention of contracts they were winning here and there, etc., but I didn't find an information motherlode, assuming such a thing exists someplace. But I didn't look very hard this last time.

Le Fri, 19 Oct 2007 13:50:27 -0700, Winfield Hill a écrit:

I just did a quick search and could find almost nothing, except this:

just because I know the full name, which is Treficable-Pirelli.

I happen to know this because some of those cables are made in France at Amfreville la Mi-Voie near Rouen, a few km away from where I lived when I was young.

Winfield Hill snipped-for-privacy@rowland.org posted to sci.electronics.design:

If i realized that you were actively looking i could have told you that their name changed to Prysmian shortly after Pirelli sold that unit.

Their competitors include ABB, Oakonite, Kerite, Plymouth Rubber and a couple others i can re-find quickly. Still interested?