电缆 额定电流的计算 第2-1部分：热阻 热阻的计算

[中文适用范围]： IEC 60287-2-1:2015 RLV 包含官方 IEC 国际标准及其红线版本。 Redline 版本仅提供英文版本，为您提供了一种快速、简单的方法来比较官方 IEC 标准与其先前版本之间的所有更改。 IEC 60287-2-1:2015 仅适用于所有交流电压和高达 5 kV 的直流电压、直接埋在地下、管道、线槽或钢管中的电缆的稳态运行条件，无论土壤是否部分干燥，以及空气中的电缆。术语“稳态”旨在表示刚好足以渐进地产生最大导体温度的连续恒定电流（100%负载系数），假设周围环境条件恒定。 IEC 60287 的这一部分提供了热阻公式。 IEC 60287-2-1 第二版取消并取代了 1994 年发布的第一版、修正案 1:2001、修正案 2:2006 和勘误表 1:2008。相对于前一版本，本版本包括以下重大技术变化： a) 引用了有限元方法的使用，其中分析方法无法用于计算外部热阻； b) SL型和SA型电缆的说明； c) 每芯有挤包绝缘和单独铜带屏蔽的非铠装三芯电缆的T3计算方法； d) 改变5.4中X的条件； e) 表 4 中包含充水管道的常数或安装条件。 [外文原描述]： IEC 60287-2-1:2015 RLV contains both the official IEC International Standard and its Redline version. The Redline version is available in English only and provides you with a quick and easy way to compare all the changes between the official IEC Standard and its previous edition. IEC 60287-2-1:2015 is solely 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, in 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 of IEC 60287 provides formulae for thermal resistance. This second edition of IEC 60287-2-1 cancels and replaces the first edition, published in 1994, Amendment 1:2001, Amendment 2:2006 and Corrigendum 1:2008. This edition includes the following significant technical changes with respect to the previous edition: a) inclusion of a reference to the use of finite element methods where analytical methods are not available for the calculation of external thermal resistance; b) explanation about SL and SA type cables; c) calculation method for T3 for unarmoured three-core cables with extruded insulation and individual copper tape screens on each core; d) change of condition for X in 5.4; e) inclusion of constants or installation conditions for water filled ducts in Table 4.