This part of IEC 60287 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. 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 part provides formulae for current ratings and losses.
The formulae given are essentially literal and designedly leave open the selection of certain
important parameters. These may be divided into three groups:
– parameters related to construction of a cable (for example, thermal resistivity of insulating
material) for which representative values have been selected based on published work;
– parameters related to the surrounding conditions, which may vary widely, the selection of
which depends on the country in which the cables are used or are to be used;
– parameters which result from an agreement between manufacturer and user and which
involve a margin for security of service (for example, maximum conductor temperature).dition 2.1 2014-11 CONSOLIDATED VERSION VERSION CONSOLIDéE colour inside Electric cables – Calculation of the current rating – Part 1-1: Current rating equations (100 % load factor) and calculation of losses – General Cables électriques – Calcul du courant admissible – Partie 1-1: Equations de l’intensité du courant admissible (facteur de charge 100 %) et calcul des pertes – Généralités IEC 60287-1-1:2006-12+AMD1:2014-11 CSV(en-fr)