IEC 60287-3-1 Ed. 1.1 b:1999

Is applicable to the conditions of steady-state operation of cables at all alternating voltages, and direct voltages up to 5 kV, buried directly in the ground, in ducts, troughs or in steel pipes, both with and without partial drying-out of the soil, as well as cables in air. This section concerns reference operatings and selection of cable type.