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Impedance of screen outer surface

Definition according to Cigré guide 531 chapter 4.2.2.5 for composite screen and sheath ($z_5$)

Symbol
$\mathscr{z}_{5,sc}$
Unit
$\Omega$/m
Formulae
$\frac{m_{z,sc} \rho_{sc}}{2\pi r_{z3,sc}} \operatorname{coth}\left(m_{z,sc} \left(r_{z3,sc}-r_{z2,sc}\right)\right)-\frac{\rho_{sc}}{2\pi r_{z3,sc} \left(r_{z2,sc}+r_{z3,sc}\right)}$
Related
$m_{z,sc}$
Parameter m of screen
$\pi$
Archimedes' constant $\pi$
$r_{z2,sc}$
Radius of screen (inner) [m]
$r_{z3,sc}$
Radius of screen (outer) [m]
$\rho_{sc}$
Specific electrical resistivity of screen material [$\Omega$.m]
Used in
$\mathscr{z}_3$
Impedance of shield inner surface [$\Omega$/m]
$\mathscr{z}_4$
Mutual impedance of shield [$\Omega$/m]
$\mathscr{z}_5$
Impedance of shield outer surface [$\Omega$/m]