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Increased tension due to pole raising

Increased tension due to pole raising

Increased tension due to pole raising

(OP)
We are looking at using phase-raiser on a transmission structure which would raise the conductor attachment points by 10'. The span is 600'. How would I determine the increase in tension in the conductor due to this change?

RE: Increased tension due to pole raising

Roughly the span has become from 600 ft to 600.0833 ft. Consider this a change ΔS=0.0833. To calculate the change in horizontal tension, if the total cable length is unchanged use
ΔH/ΔS ≈ 12·H³/(S³w²)
where H is the horizontal tesion, w is the linear weight and S is the horizontal span.

Of course this is an aproximation, as the cable will stretch more with the increased tensions. To get an accurate result you need a proper sag & tension software.

John Alexiou
Alcoa Design Engineer
MSME Georgia Tech

RE: Increased tension due to pole raising

Can't verify the above equation, but tried an example and the results did not seem to be even be in the right ball park so I may have entered something wrong.

For 5 or 10 foot changes in structure height on spans that long, I don't think most would even consider the change in tension.  If you are a PLS-CADD user with the SAPS feature, there is a routine  in there to do just what you are considering.

If you are not on level ground, the tension may increase or decrease, depending on the pole being raised.

RE: Increased tension due to pole raising

(OP)
Thanks for the help!

I have Sag10, is there a way to get an accurate answer using it?

If not, I might try sending it to one of our other offices that has PLS-CADD.

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