Thermal resistance of jacket

Symbol
$T_3$
Unit
K.m/W
Formulae
$\frac{\rho_j}{2\pi} \ln\left(\frac{D_e}{D_e-2t_3}\right)$General case
$1.6T_3$(part-)metallic sheathed single-core cables in trefoil formation
$\frac{1}{2k_{prot} \pi} \ln\left(\frac{D_{prot}}{D_{encl}}\right)$PAC/GIL