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Equivalent thermal resistance

Equivalent thermal resistance per conductor.

Symbol
$T_{eq}$
Unit
K.m/W
Formulae
$T_1+n_{ph} \left(\left(1+\lambda_1\right) T_2+\left(1+\lambda_1+\lambda_2+\lambda_3\right) T_3\right)+n_{cc} \left(\left(1+\lambda_1+\lambda_2+\lambda_3\right) \left(T_{4i}+T_{4ii}+v_4 T_{4\mu}\right)+\lambda_4 \left(\frac{T_{4ii}}{2}+v_4 T_{4\mu}\right)\right)$cable
$T_{hs}+T_{4iii}$heat source
Related
$\lambda_1$
Loss factor of shield (screen and sheath)
$\lambda_2$
Loss factor of armour
$\lambda_3$
Loss factor of steel pipes for pipe-type cables
$\lambda_4$
Loss factor of magnetic steel ducts
$n_{cc}$
Number of conductors combined
$n_{ph}$
Number of phases in a cable
$T_1$
Thermal resistance between one conductor and sheath [K.m/W]
$T_2$
Thermal resistance of armour bedding [K.m/W]
$T_3$
Thermal resistance of jacket [K.m/W]
$T_{4i}$
Thermal resistance of medium in the duct [K.m/W]
$T_{4ii}$
Thermal resistance of the duct wall [K.m/W]
$T_{4iii}$
Thermal resistance to ambient [K.m/W]
$T_{4\mu}$
Thermal resistance to ambient [K.m/W]
$T_{hs}$
Thermal resistance of heat source [K.m/W]
$v_4$
Ratio thermal resistivity dry/moist soil
Used in
$\gamma_X$
Attenuation factor for crossing [1/m]