Cableizer ®

Thermal resistance armour bedding

Thermal resistance of the bedding between sheath and armour consists of the bedding between the sheath and the first armour layer plus the separation material between the first and second armour layer if any. In case of three-core cables with jacket around each core, this is the thermal resistance of the filler between sheath and armour for three-core cables type SS with sheath. This includes the thermal resistance of the jacket around each core and of the armour bedding.

Symbol
$T_2$
Unit
K.m/W
Formulas
$\frac{\rho_{ab}}{2\pi} \ln\left(1+\frac{2t_2}{D_{sh}-\left(H_{sh}+\Delta H\right)}\right)$Single-core cables or multi-core cables with common sheath
$\frac{\rho_f}{6\pi} G_2$three-core cables type SS with sheath or type SS/SC without sheath with tape screen
$\frac{1}{3} \frac{1}{F_{lay,3c}} \frac{\rho_{shj}}{2\pi} \ln\left(1+\frac{2t_{shj}}{D_{sh}-\left(H_{sh}+\Delta H\right)}\right)+\frac{\rho_f}{6\pi} G_2$CIGRE TB 880 Guidance Point 45, three-core cables type SS with sheath + jacket over each core
$T_{spf}+T_{ab}$pipe-type cables
$T_{scs}+T_{dsh}$CIGRE TB 880 Guidance Point 15, cables with screen, with sheath, without armour
$T_{scs}+T_{dsh}+T_{ab}$CIGRE TB 880 Guidance Point 15, cables with screen, with armour
$T_{ab}$CIGRE TB 880 Guidance Point 15, cables without screen, without sheath, with armour
$T_{ab}$CIGRE TB 880 Guidance Point 15, cables without screen, with sheath, with armour
$0$CIGRE TB 880 Guidance Point 15, cables otherwise
Related
$D_{sh}$
Diameter over sheath [mm]
$\Delta H$
Correction depth of corrugation [mm]
$F_{lay,3c}$
Effective length per unit lay length twisted conductors
$G_2$
Geometric factor $G_2$ cables with separate sheaths
$H_{sh}$
Depth of corrugation [mm]
$\pi$
Archimedes' constant $\pi$
$\rho_{ab}$
Thermal resistivity armour bedding [K.m/W]
$\rho_f$
Thermal resistivity filler [K.m/W]
$\rho_{shj}$
Thermal resistivity sheath jacket material [K.m/W]
$t_2$
Thickness sheath—armour [mm]
$T_{ab}$
Thermal resistance armour bedding [K.m/W]
$T_{dsh}$
Thermal resistance corrugation filling [K.m/W]
$T_{scs}$
Thermal resistance screen serving [K.m/W]
$t_{shj}$
Thickness sheath jacket [mm]
$T_{spf}$
Thermal resistance steel pipe filling [K.m/W]
Used in
$\Delta \theta_{dj}$
Temperature rise dielectric losses $\rightarrow$ cable surface [K]
$I_c$
Conductor current [A]
$Q_{B,ab}$
Thermal capacitance B transient thermal circuit, armour bedding [J/(m.K)]
$Q_{B,f}$
Thermal capacitance B transient thermal circuit, filler [J/(m.K)]
$R_{c3}$
Thermal resistance part 3 [K.m/W]
$T_B$
Thermal resistance B transient thermal circuit [K.m/W]
$T_d$
Internal thermal resistance for dielectric losses [K.m/W]
$T_{eq}$
Thermal resistance, equivalent [K.m/W]
$T_{int}$
Internal thermal resistance for current losses [K.m/W]
$T_r$
Thermal resistance, total [K.m/W]
$T_{tot}$
Thermal resistance, transient [K.m/W]
$\theta_{ar}$
Temperature armour [°C]
$\theta_{c,z}$
Temperature conductor z [°C]
$\theta_e$
External temperature object [°C]
$\theta_f$
Temperature filler for multi-core cables type SS with sheath [°C]
$\theta_{sp}$
Temperature steel pipe [°C]