Mean distance between the phases

This is the geometric mean distance (GMD) between phases.

Symbol
$a_m$
Unit
mm
Formulae
$L_{earth}$single-phase system
$s_c$two-phase system
$\left(a_{12} a_{23} a_{31}\right)^{\frac{1}{3}}$three-phase system
Used in
$X_c$
$X_{S1}$
Reactance section 1 [$\Omega$/m]
$X_{S2}$
Reactance section 2 [$\Omega$/m]
$X_{S3}$
Reactance section 3 [$\Omega$/m]