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Formula for sag on power lines

  • 20-05-2009 7:28pm
    #1
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,641 Mod ✭✭✭✭


    Hi does anyone have the formula for calculating the sag on power lines??? Thanks:)


Comments

  • #2
    mathew
    Registered Users, Registered Users 2 Posts: 1,488 ✭✭✭mathew


    Dont they follow a cosh wave pattern..

    This what your looking for? http://www.scribd.com/doc/12736614/Sag-Tension-Calculation


  • #3
    Michael Collins
    Moderators, Science, Health & Environment Moderators Posts: 1,852 Mod ✭✭✭✭Michael Collins


    mathew wrote: »
    Dont they follow a cosh wave pattern..

    This what your looking for? http://www.scribd.com/doc/12736614/Sag-Tension-Calculation

    Yeh it's called a Catenary. How accurate this is probably depends on the stiffness of the cable - the stiffer the cable, the less like a catenary it will be.


  • #4
    enmac
    Registered Users, Registered Users 2 Posts: 98 ✭✭enmac


    2011 wrote: »
    Hi does anyone have the formula for calculating the sag on power lines??? Thanks:)

    parabola formula is good for spans up to 600 metres

    sag= L squared/ 8c

    L = span length
    c= catenary constant = T/w

    T= tension of conductor - newtons
    w= mass of conductor per unit length (kg/m) x 9.8

    eg.
    conductor weight 2.22kg/metre
    tension 35.8 kN
    span 300 metres

    sag = 6.84metres


    if you use the catenary equation (cosh function) instead of the parabola you would get a sag of 6.85metres


  • #5
    SparkyLarks
    Registered Users, Registered Users 2 Posts: 363 ✭✭SparkyLarks


    http://docs.cpuc.ca.gov/published/graphics/13352.pdf
    lot of good info here,

    The California State Rules on overhead line construction


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