Droop Cable

Status
Not open for further replies.
N

nkalghatgi

Member
Location
Mechanicsburg, PA, USA
How to accurately find the length of a droop aerial cable which is connected between 2 points at different elevations. There is a function in AutoCAD known as CAT used for catenary cables but it asks for too many things which I am not sure how to calculate like cable tension. Any help would really be appreciated.
 
nkalghatgi said:
How to accurately find the length of a droop aerial cable which is connected between 2 points at different elevations. There is a function in AutoCAD known as CAT used for catenary cables but it asks for too many things which I am not sure how to calculate like cable tension. Any help would really be appreciated.
Click to expand...
The cable tension is something you need to supply since it will determine the amount of the droop. You can put in a maximum value to get the minimum droop of you can put in a smaller number for more droop. Once you get the droop in feet that you like, based on clearances, appearance, etc. it will tell you the extra length of the cable beyond the straight line distance.
 
nkalghatgi said:
Thank you, for your quick response, but how do I find the cable tension based on the weight of the cable.
Click to expand...
You do not. You find out the maximum tension the cable can hold and the maximum tension that the attachment point can support and plug that in for a start, then lower it a whole lot until you see the droop in feet that you want.
The tension depends very strongly on the amount of droop, or vice versa. Over a wider range than the weight of the cable.
 
It's still and arc, which still means it part of a circle.

Not negating any code requirement you might need to meet.

(i beleive) the 11th or the 12th diagrams shown here. (from left to right)
In XO = 0 X1= travel distance (horizontal), Y0 = start elevation and
Y1= finish. I didn't insert numbers to proof it.

Google Image

Hope this helps!
 
Only general prinicples of physics here, never saw second level w/calculus involved.

Thanks for the information, I try so hard to choose the correct words and expressions!

:D
 
For those of you who love calculus: The curve of a wire or chain under only its own weight is a catenary, from the latin word for chain.
The curve for a suspension bridge cable where the weight is uniform over the horizontal distance is our old friend the parabola.
But for a droop which is small compared to the length, they all work out close enough for your purposes. Just make the cable a little long and cut to fit
:)

Sent from my XT1080 using Tapatalk
 
The cable droop will also need to take into consideration the loading on the cable. As it heats up from current flow it will sag.

There are programs that transmission line designers use that calculates all this.
 
Status
Not open for further replies.
Top