Mutual impedance between conductor and metal screen

Mutual impedance between phase conductor and metal screen of a cable with earth return according to the Cigré guide 531 chapter 4.2.3.6. The mutual reactance between the conductor and the sheath is equal to the sheath reactance $X_s$ when the conductor is concentric within the sheath.

Symbol
$Z_{m}$
Unit
$\Omega$/m
Formulae
$R_{earth} + 1.0 i X_{s}$