Mutual impedance armour

Definition according to CIGRE TB 531 chap. 4.2.1

Symbol
$\mathcal{Z}_{pmut}$
Unit
$\Omega$/m
Formulas
$\frac{m_{z,ar} \rho_{ar}}{\pi \left(r_{z4}+r_{z5}\right)} \frac{1}{sinh\left(m_{z,ar} \left(r_{z5}-r_{z4}\right)\right)}$