Geometric mean radius of conductor

The formula for round conductors was taken from the book 'Electric Power Generation, Transmission, and Distribution' by Leonard L. Grigsby (2006), chapter 14.1.2.3.

The formula for shaped conductors was taken from the paper 'Series impedance of distribution cables with sector-shaped conductors' by Andrew J. Urquhart (2015)

Symbol
$GMR_c$
Unit
mm
Formulae
$K_{GMR} r_c$round conductors
$e^{\frac{-1}{4}} \sqrt{\frac{A_c}{\pi}}$shaped conductors