Impedance conductor outer surface

Definition according to Cigre TB 531 chap. 4.2.1

Symbol
$\mathscr{z}_1$
Unit
$\Omega$/m
Formulas
$\frac{m_{z,c} \rho_c}{2\pi r_{z1}} \operatorname{coth}\left(0.777m_{z,c} r_{z1}\right)+\frac{0.356\rho_c}{\pi {r_{z1}}^2}$hyperbolic function
$\frac{m_{z,c} \rho_c}{2\pi r_{z1}} \frac{\operatorname{i0}\left(m_{z,c} r_{z1}\right)}{\operatorname{i1}\left(m_{z,c} r_{z1}\right)}$Bessel function
Used in
$\mathscr{z}_{cc}$
Impedance conductor [$\Omega$/m]
$\mathscr{z}_{int}$