# Transient thermal resistance for daily load

Effective transient thermal resistance in the earth for a transient period of $\tau$. The used equations ensure that the transient thermal resistance cannot become negative for very short transient periods.

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

Symbol
$T_{4d}$
Unit
K.m/W
Formulae
 $\frac{\rho_{4} \ln{\left(\frac{\operatorname{Max}{\left(D_{x},Do_{d} \right)}}{Do_{d}} \right)}}{2 \pi}$ buried $\frac{\rho_{4} \ln{\left(\frac{\operatorname{Max}{\left(D_{x},Do_{t} \right)}}{Do_{t}} \right)}}{2 \pi}$ in trough
Related
$D_{x}$
$Do_{d}$
$Do_{t}$
$\rho_{4}$
$T_{4w}$
$T_{4y}$
$\tau$
Used in
$T_{4\mu}$