What is the criteria for selecting sheath of the underground cables?

Underground power cables must give a service life of at least 20-25 years whilst carrying the expected load and overload currents without overheating under worst case ambient and ventilation conditions, simultaneously withstanding mechanical pulling stresses during installation, and radial stresses during their operating life

It can be selected through the type of land/soil where cables be laid.

Depending upon the Insulation level required, the Selection of the Sheath can be determined.