Agreed. For slack spans the difference becomes more apparent. I was trying to be consistent in an Excel Sag-Tension app that uses the hyperbolic form for all calcs except finding an initial tension with a given sag.
The City of Seattle Municipal Utility (SCL) used 26.4kV subtransmission to serve 4kV unit subs in the '30's. After WWII transformer mfgs. figured out how to build a 15kv L-G pole top transformer so SCL started to use 26.4 distribution in the early '60's. A few other utilities also use the same...
The parabolic equation for wire sag is S = W x L x L /(8 x T) where S=sag (ft), W=wire weight (lb/ft), L=Span (ft), and T =wire tension (lb).
Tension can be expressed by T = W x L x L /(8 x S).
The more accurate hyperbolic form for sag is S = (T/W) x {cosh[W x L/(2 x T)]-1}.
Does anyone know of...
