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?
Roughly the span has become from 600 ft to 600.0833 ft. Consider this a change [Δ]S=0.0833. To calculate the change in horizontal tension, if the total cable length is unchanged use
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
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.