John Valdes

My neighbor and I were discussing what the bare medium and high voltage transmission lines strung overhead are made of. He thought it was aluminum. I do not think aluminum is strong enough for the high physical tension. Could it be made of an alloy? Thanks

brian john

Last night on the History Channel they said the conductors were steel and/or Aluminum. I would surely think some kind of aluminum alloy

MDShunk

Yeah, it's aluminium, but the actual stresses are taken up by steel strands in the middle, just like the neutral of ACSR. I have some chunks in a storage trailer of transmission conductors, so I'll take a few pics one day next week.

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Joe Momma

I played with a few pieces that were laying around on a job. They were very light weight so definetely aluminum, but very difficult to bend so I'm guessing a specific alloy.
Didn't notice if there was a steel strand, but by how surprisingly light weight they were I'm thinking there wasn't.

And I watched that episode of modern marvels last night too

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Joe Momma was here

LightGuy48

I don't know if all transmission lines are this way but the big really large ones are aluminum with a steel core due to the weight of the cable between the towers and also the wind and possible ice loading.

I saw this on a show that I believe was on the History channel where they sent a guy up with a complete Faraday body suit to X-Ray the lines hot due to a tornado that crossed the path of the tranmission lines. They were checking to see if the steel core had been damaged by the excessive wind load where the cabling passed through the saddle at the insulators.

They said it was the first time they had attempted to X-Ray an energized line and it apparently worked just fine.

micromind

I've done linework, they're aluminum with usually one, sometimes more steel strands in the middle. You can't cut them with standard cable cutters, it'll nick the blades. The ones I use are alot like bolt cutters.

The size is strange, there's the normal 1/0 and such, but over 4/0 it gets weird. Like 397 and 477 MCM. I have no idea how this came about.

Splicing is different as well, most of the crimp tools I've seen for inside wire are 8-15 tons, and larger sizes you crimp more than once. On overhead lines, the tools are sized to the wire, the last 477 I did (several years ago) used a 100 ton tool, (it takes 2 guys just to lift the head in place) and the crimp sleeve was about 8" long. Just one crimp. The die doesn't exactly fit the sleeve, it crimps harder in the middle than the outsides.

LightGuy48

I'm curious, any idea what the tensile strength of the cables are, also what about the splices before they would separate?

MDShunk

The splices are stronger than the conductor. They're called "full tension splices". The tensile strength depends on the gauge and the temperature, but it can be in the 10's of thousands of pounds.

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Bkessler

I always make sure to borrow some one elses cutters when I cut overhead wires! Is that steel wire in the middle not called the messenger cable?

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When ls lunch

LightGuy48

It's my understanding that yes it would technically be the messenger cable as it high strength steel cable, which by the definitions I've seen can either be integrated into the cable or external to it (such as telco, cable TV, and fiber lines)

brian john

Multi strand locomotive cable is manufactured in off sizes as well 375 KCMIL, 535 KCMIL.

micromind

Also, you have to be careful when selecting crimp lugs for locomotive cable. For example, you'd think a 600 lug would fit a 535 cable....well, it sort of will, but you'll have to pound it on, and hope none of the strands sneak out. Actually, the lug manufacturers have approved locomotive cable sizes that aren't the normal ones. For example, 535 will use a 700 lug. If you look at the charts, and use the proper lug, it works well. Just sort of strange to use an oversize lug.

Alot of this type of cable has "Diesel Locomotive Cable" printed on the jacket, I've always wondered what would happen if you used it on a gas locomotive, or a propane one. lol. Would the electrons actually know the difference? lol. Sorry, strange sense of humor here!

frenchelectrican

The other thing to head up with the " DLC " Diesel Locomovite cable is that they are useally dual rated for 600 and 1500 volts as well i work on diesel locomovites from time to time basically they are megasized generators on steel wheels with electric traction motors

yeah they are oddball size connections and they are much more finer stranded than standard run of mill THHN/THWN building wires.

once a while i heard someone will use the DLC to replace some of the nonstandard MTW wires and IIRC they are 105 or 150°C rated conductors as well if the facts stand correct.

Merci, Marc

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Pas de problème,il marche n'est-ce pas?"(No problem, it works doesn't it?)

MDShunk

I sometimes use DLO cable in and out of transformers. It bends so much nicer to get where it needs to be. I'm sure that's not an approved use, but I do it anyhow. The specs are superior to THHN anyhow.

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frenchelectrican

Yep that work as well but my inspectors dont like the idea sometime they will " growls " at me

Merci, Marc

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Pas de problème,il marche n'est-ce pas?"(No problem, it works doesn't it?)

gilbequick

Ok I give, what is locomotive cable?

micromind

DLO cable is alot like welding leads; a huge number of very small strands. It's very flexible, and has thick rubber insulation.

I use it alot to connect generators, motors, and xfmrs. Easy to bend in tight spaces, and abrasion resistant.

Because it's flexible, it doesn't loosen up in set-screw lugs, and doesn't transmit mechanical stress to what it's connected to.

It's quite expensive, and doesn't pull well in conduit, especially PVC.