Effective transient thermal resistance in the earth:

The transient component of the heat flow will penetrate the earth only to a limited distance from the cable, thus the corresponding thermal resistance $T_{4et}$ will be smaller than its steady-state counterpart. It is assumed that the temperature rise over the internal thermal cable resistance is complete by the end of the transient cycle.

Symbol
$T_{\mathrm{4et}}$
Unit
K.m/W
Formulae
$\frac{\rho_{\mathrm{4}}}{2 \pi} \ln{\left (\frac{D_{\mathrm{x}}}{Do_{\mathrm{d}}} \right )}$
Related
$D_{\mathrm{x}}$
$Do_{\mathrm{d}}$
$\rho_{\mathrm{4}}$
Used in
$T_{\mathrm{4\mu}}$