Mutual impedance of armour

Definition according to Cigré guide 531 chapter 4.2.1, analogue to parameter $z_4$ for screen.

Symbol
$z_{ar,m}$
Unit
$\Omega$/m
Formulae
$\frac{1\frac{m_{e67} \rho_{ar}}{\pi \left(r_{e6}+r_{e7}\right)}}{sinh\left(m_{e67} \left(r_{e7}-r_{e6}\right)\right)}$