1 more voltage drop thread

[Mayimbe]

According to Brice (1982), the voltage drop for distribution systems is:

Vd=Ir*R+Ix*X

where

Ir = I cos (theta)... etc...

my questions are, do the X value depends on the insulation type or thickness?,
is there tables for the X values?,
do these X values have the contribution of the inductive and capacitive reactances?

i have heard that for underground conductors the capacitive reactance is not neglectable as in overhead lines...
i got a 480 V, 472.5 Amp, 600 kcmil, direct buried conductor.

i have seen the other voltage drops question but didnt find this aproach, everybody assumes that pf = 1, whys that?

thanks in advance