This is the conductor temperature rise above the ambient temperature caused by dielectric losses respectively above the cable oversheath temperature for cables in tunnel.

The temperature rise caused by dielectric losses is important for high-voltage cables because they are strongly voltage dependent. If the application of system voltage occurs, then an additional transient temperature rise due to the dielectric loss has to be calculated with following assumptions:

Symbol
$\Delta \theta_{\mathrm{d}}$
Unit
K
Formulae
$W_{\mathrm{d}} \left(T_{\mathrm{d}} n_{\mathrm{c}} + n_{\mathrm{cc}} \left(T_{\mathrm{4i}} + T_{\mathrm{4ii}} + T_{\mathrm{4iii}}\right)\right)$cables in air
$W_{\mathrm{d}} \left(T_{\mathrm{d}} n_{\mathrm{c}} + n_{\mathrm{cc}} \left(T_{\mathrm{4i}} + T_{\mathrm{4ii}} + T_{\mathrm{4\mu}}\right)\right)$buried cables
$W_{\mathrm{d}} \left(T_{\mathrm{d}} n_{\mathrm{c}} + n_{\mathrm{cc}} \left(T_{\mathrm{4i}} + T_{\mathrm{4ii}}\right)\right)$cables in tunnel
$W_{\mathrm{d}} \left(T_{\mathrm{4t}} n_{\mathrm{cc}} + T_{\mathrm{d}} n_{\mathrm{c}}\right)$cables in tunnel (IEC 60287-2-3)
Related
$n_{\mathrm{c}}$
$n_{\mathrm{cc}}$
$T_{\mathrm{4ii}}$
$T_{\mathrm{4\mu}}$
$W_{\mathrm{d}}$
Used in
$\Delta \theta_{\mathrm{R_{\mathrm{\infty}}}}$
$\Delta \theta_{\mathrm{s}}$
$I_{\mathrm{c}}$
$r_{\mathrm{\theta}}$