cable loads
cable loads
(OP)
What methods are used to calculate the end loads exerted by transmission cables on the towers?
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RE: cable loads
ALCOA's SAGTEN program is one of several programs that deal with wire sag and tensions. There are also many books addressing the subject...Structural Engineering Handbook, by Gaylord & Gaylord; The Catenary & Overhead Lines, by Sagline Inc. (914-248-8001?); RUS Bulletin 1724E-200 to name a few.
For a level span, the tension at the point of support is equal to the horizontal tension plus the unit weight of the conductor times the sag in the conductor (T = Th + Wc*S).
That's a five minute answer to a week long seminar.
RE: cable loads
Thanks! I did find out about the parabolical/catenary issues.
RE: cable loads
These are just half the story in transmission lines. The most important part is the cable behavior (stress-strain curves and creep rate). A lot of people assume a linear model of aerial cables which often gives erroneous results. Alcoa has historically used 4th order polynomials for the stress-strain curves.
If you want more information on sag10, or the alcoa graphical method please email me, or visit www.sag10.com
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John Alexiou
Product Development Engineer - SAG10/Vibrec
Alcoa.
RE: cable loads
"Just an opinion"
A cable must be completley flexable to hang in a true catenary. Line conductors a very stiff and do not hang in a true catenary. A chain would probably be very close to a true catenary. I believe catenary is latin for chain? So, what curve does a cable hang in? My guess is somewhere between a parabola and a catenary. I have not seen any reasearch on this so I ass_u_me that the catenary is close enough.
Measure with a micrometer, mark with chalk, cut with an ax.
Kevin
RE: cable loads
E^2*I^2+2*E*I*T*a^2+T^2*a^4-a^6*w^2=0. So the hanging cable with flexular rigidity is no different from a beam with axial loading.
Ref. T=tension, w=linear weight, E=modulus of elasticity, I=2nd moment of area,
John Alexiou
Alcoa Design Engineer
MSME Georgia Tech