IEC 60287-3-1:2017 is applicable to the conditions of steady-state operation of cables at all voltages, 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. The term "steady state" is intended to mean a continuous constant current (100 % load factor) just sufficient to produce asymptotically the maximum conductor temperature, the surrounding ambient conditions being assumed constant. This document defines site reference conditions, however the general values are superseded by specific national requirements. This edition includes the following significant technical changes with respect to the previous edition:
- the updated list of national laying conditions is now covered in Annex A;
- Clause 5 about the information required from the purchaser for the selection of the appropriate type of cable has been removed.