AC distribution tower wire denotation/ arrangement.

Discussion in 'General Electronics Chat' started by supermankid, Jul 24, 2015.

  1. supermankid

    Thread Starter Member

    May 26, 2013
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    I did some research on AC distribution system. It is amazing how they maintain constant voltage and
    frequency from the generator.
    I couldnot find good informaton on the transmission towers though!!!
    They carry three phase current but why are there 6 or so hangers as shown in the picture attached?
    and on one hanger there is again bunch of wires.
    Could someone explain the wires arrangement in AC distribution towers or provide link to good source.
    Thanks in advance.

    pylon_ds_1024.jpg

    Moderators note: reduced image size
     
    Last edited by a moderator: Jul 24, 2015
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    FWIW: I can but assume the pylons are carrying two 3-phase 'lines'
     
  3. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the "groups" of wires on each insulator are carrying the same phase, just paaralelled for more current carrying. the six conductors are just three phase with two circuits. the four wires per phase allow for more current with less weight than one larger conductor. and less heating of the conductor.
     
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  4. sirch2

    Well-Known Member

    Jan 21, 2013
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    I'm intrigued as to what the word "detonation" in the subject should have been... "designation" perhaps?
     
  5. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Indeed! Intriguingly the 'skin effect' (q.v.) comes into play at even ELF... Hence surface area often 'trumps' (or seriously 'competes' with) cross section...
     
    Last edited: Jul 24, 2015
  6. crutschow

    Expert

    Mar 14, 2008
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    And the center of the cable is usually steel for strength, so carries little of the current anyway.
     
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
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    which would have more surface, 4 conductors spaced apart paralelled, or one with the same amount of copper? and skin effect usually is considered to be a problem above 100 khz or so. which would have more air cooling effect? around here there is usually two paralled conductors around 1.25 inch thick or so. on the 354 kv lines. they start with single conductor, and then add more as the load increases.
     
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  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    When I was but a wee lad in power generation and distribution class, 765 kV lines still were fairly new. Obviously, a single conductor could replace the four conductors in a box, but it would arc into the atmosphere. For the same operating voltage and current, the box arrangement is lighter, has a lower wind load, and a much higher arc potential. In terms of calculating its ability to arc or not arc, the box has the same effective diameter as a single conductor with a diameter equal to the diagonal of the box.

    Each of the cables is ACSR - Aluminum conductor, steel reinforced. The lower power sample I remember had steel aircraft cable down the center, oiled paper spiraled around that, a layer of aluminum conductors spiraled around that, then the outer jacket. Today's are bigger.

    https://en.wikipedia.org/wiki/Aluminium-conductor_steel-reinforced_cable

    ak
     
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  9. crutschow

    Expert

    Mar 14, 2008
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    4 paralleled. That's why they use Litz wire at high frequencies.

    The skin depth at 60Hz [current drops to 1/e (37%) of the surface value] is 0.36" which is much less than the radius of the transmission line wires.
     
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