Mutual impedance of screen

Definition according to Cigré guide 531 chapter 4.2.2.5 for composite screen and sheath ($z_4$)

Symbol
$\mathscr{z}_{4,sc}$
Unit
$\Omega$/m
Formulae
$\frac{m_{z,sc} \rho_{sc}}{\pi \left(r_{z2,sc}+r_{z3,sc}\right)} \frac{1}{sinh\left(m_{z,sc} \left(r_{z3,sc}-r_{z2,sc}\right)\right)}$
Used in
$\mathscr{z}_3$
$\mathscr{z}_4$