# Loss factor of armour

The formulae express the power loss occurring in metallic armour, reinforcement of steel pipes of a cable in terms of an increment $\lambda_2$ of the power loss in all conductors. The IEC standard has formulae for three distinctive cases: Non-magnetic armour or reinforcement, Magnetic armour or reinforcement, and losses in steel pipes.

To be noted:

• When there is no armour present, then $\lambda_2=0$.
• The equation for steel tape armour is only valid for steel tapes between 0.3 and 1.0 mm thickness.
• For one-phase systems, armour loss factor is not calculated ($\lambda_2=0$).

Symbol
$\lambda_{2}$
Formulae
 $\frac{R_{s} \lambda_{1}}{R_{A} + R_{s}}$ non-magnetic armour $\frac{R_{s} W_{sA}}{W_{c} \left(R_{A} + R_{s}\right)}$ magnetic armour, multiple single-core cable $\frac{9.13614362192894 \cdot 10^{-9} A_{a} \omega \left(r_{c} + 0.675675675675676 t\right)^{2}}{R_{c} \left(A_{a} + 0.0104493207941484 d_{a}^{2}\right)^{2}} + \frac{6.2 \cdot 10^{-15} \omega^{2}}{R_{A} R_{c}}$ magnetic armour, two-core cable $\frac{1.64 R_{A} s_{c}^{2}}{R_{c} d_{a}^{2} \left(\frac{7672900000000.0 R_{A}^{2}}{\omega^{2}} + 1\right)}$ magnetic steel wire armour, three-core cable, round conductors $\frac{0.358 R_{A} d_{c}^{2}}{R_{c} d_{a}^{2} \left(\frac{7672900000000.0 R_{A}^{2}}{\omega^{2}} + 1\right)}$ magnetic steel wire armour, three-core cable, sector-shaped conductors $\frac{4.0 \cdot 10^{-11} f^{2} s_{c}^{2} \left(0.225 \delta _{ar} + \frac{1}{\delta _{ar}}\right)}{R_{c} d_{a} \left(\frac{d_{a}}{\delta _{ar} \mu_{s}} + 1\right)^{2}}$ magnetic steel tape armour, three-core cable $\lambda_{2} \left(- \frac{0.666666666666667 R_{c} \lambda_{1cb}}{R_{s}} + 1\right)$ magnetic armour, three-core cable, individual screen/sheath $\frac{R_{A} W_{A}}{W_{c}}$ magnetic armour but without screen/sheath $0$ otherwise
Related
$A_{a}$
$d_{a}$
$d_{c}$
$\delta _{ar}$
$\omega$
$R_{c}$
$r_{c}$
$s_{c}$
$W_{A}$
$W_{c}$
$W_{sA}$
Used in
$f_{SHF}$
$I_{c}$
$T_{eq}$
$T_{i}$
$\theta_{c_{z}}$
$W_{A}$
$W_{h}$
$W_{I}$
$Z_{pos}$