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Factor $F_{ar}$ for armour losses

The addition of steel tape armour increases the eddy-current loss in the sheath. The values for $\lambda_{12}$ given in IEC 60287-1-1, clause 2.3.7 and 2.3.8 should be multiplied by the following factor.

We consider this factor not only for steel tape armour but also for cables with steel wire armour. This corresponds to the procedure made in the paper 'Effective assessment of electric power losses in three-core XLPE cables' by Ander Madariaga et al., dated 2013.

Symbol
$F_{ar}$
Formulae
$\left(1+\frac{1\left(\frac{d_{sh}}{d_{ar}}\right)^2}{1+\frac{d_{ar}}{\mu_s \delta_{ar}}}\right)^2$
Related
$d_{ar}$
Mean diameter of armour [mm]
$d_{sh}$
Mean diameter of sheath [mm]
$\delta_{ar}$
Equivalent thickness of armour [mm]
$\lambda_{12}$
Loss factor of shield by eddy currents
$\mu_s$
Relative permeability
Used in
$\lambda_{12}$
Loss factor of shield by eddy currents