This formula may be used to estimate a for a catenary whose span and sag are known, if the sag is not too large. Note that it can also be found by taking moments about a point of support, where Hb = wx2/2.

https://mysite.du.edu/~jcalvert/math/catenary.htm

This property constrains the vertical sag to be a certain fraction of the horizontal span length. If the span length is changed, the sag fraction will be held constant. For example, setting the sag ratio to 2% will yield a 2m sag for a 100m span, which will grow to 3m if the span is lengthened to 150m.



In these cases, unlike with the tension constraints (HT and MT), the tension may be significantly different for different span lengths.



Given the assumption of equalising tensions, in the case where a conductor has multiple spans of uneven length, it is not possible to constrain them all to the same sag/span ratio. Instead, PLP derives the tension for a hypothetical level span with length equal to the ruling span, as a best-effort compromise. In practice this means:

For lengths shorter than the ruling span, the resulting sag to span ratio will be slightly smaller than the specified sag to ruling span ratio.
For lengths longer than the ruling span, the resulting sag to span ratio will be slightly larger than the specified sag to ruling span ratio.


If the user needs each span to reflect the sag to span ratio exactly, the conductor should be broken up into individual spans, each strained separately. This can be accomplished with the split tool. This allows the horizontal tensions to be treated as unbalanced under temperature change.

https://powerlinespro.freshdesk.com/support/solutions/articl...

The dip of the conductor between the two level supports is called sag. In other words, the vertical distance between the highest point of the electrical pole or tower (where the conductor is connected) and the lowest point of the conductor between the two adjacent level supports is known as sag shown in the figure below. The horizontal distance between two electrical supports is called the span.

https://circuitglobe.com/sag-and-tension.html

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Note added at 4 hrs (2019-06-05 09:27:36 GMT)
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I have a low confidence level because I can't find an equivalent term. Explained in layman's terms by someone who's definitely not an expert on the subject, saeta is the vertical line between the lowest point of the catenary and the height of the lowest support. Flecha is the vertical line between the lowest point of the catenary and the height of the highest support.

If you look at the reference I include in the reference box, you'll see diagrams showing saeta and flecha. Try googling sag calculations or catenary calculations/coordinates and you might have more luck than me.