scope:

Commented versions are a valuable improvement upon the conventional IEC Redline Version (RLV). These versions are designed to facilitate a clearer understanding of the revisions made between the prior and current editions of a publication. This enhanced product package incorporates both the most recent edition of the document and the annotated redline version. This combined offering provides users with an easily accessible means to track and comprehend the alterations and additions that have been made, thereby enhancing the utility and effectiveness of the publication for its intended audience.

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 document provides formulae for current ratings and losses.

The formulae given are essentially literal and designedly leave open the selection of certain important parameters. These can 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 can vary widely, the selection of which depends on the country in which the cables are used or will 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).