Formula for sag on power lines

20-05-2009 08:28PM #1

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

mathew · 20-05-2009 08:37PM

Dont they follow a cosh wave pattern..

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

Michael Collins · 20-05-2009 10:27PM

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.

enmac · 22-05-2009 11:45PM

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

SparkyLarks · 31-05-2009 08:11PM

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

The California State Rules on overhead line construction

Formula for sag on power lines

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