Skin effect factor of conductor

In the absence of alternative formulae, it is recommended that the formulae should be used for sector and oval-shaped conductors.

Symbol
$y_s$
Formulae
$\frac{{x_s}^4}{192+0.8{x_s}^4}$$x_s<=2.8$
$0.354x_s-0.733$$x_s>3.8$
$0.0563{x_s}^2-0.0177x_s-0.136$otherwise