Transient load period for deep burial

The input and output is made in years, while the calculation is made in seconds, with 1 year = 365.25 days and 1 day = 86400 seconds.

For soils with a thermal diffusivity varying from 0.35e-6 to 1.2e-6 m2/s a soil layer with a depth of about 100 m results in a time constant of 30 to 100 years (refer to the book Sustainable Energy Technologies, chapter 9.3.1, by E. Rincon-Mejia, 2008). For a typical life time of an XLPE cable, count with a $\tau_L$ of 40 years.