IEC 60287-1-2:20 23提供了一种计算布置为扁平结构的三相双回路的单芯电缆金属护套中涡流损耗的方法。鞘在一点处结合或交叉结合，使得没有显著的鞘循环电流。当金属护套在两端结合时，存在显著的循环电流，这导致较低的载流能力。IEC 60287-1-3中提供了一种计算双回路环流损耗的方法。 本文中描述的方法提供了用作对一个隔离的三相电路的护套的损耗因子的校正的系数。对于其中参数m小于大约0.1(m=ω/(Rs·107))的电缆，这些校正是可以忽略的，这对应于在50Hz下高于314 μ Ω/m的护套纵向电阻。因此，该方法用于大多数尺寸的铝护套电缆，但不需要用于铅护套电缆，除非它们异常大。 这些系数以表格形式提供，并且已经根据护套损耗的基本公式计算出来，其评估需要计算机编程方面的专业知识，这在一般商业情况下可能不容易获得。正在考虑为一些列表系数制定简化公式。 IEC 60287-1-1涵盖了单个电路中电缆的损耗。

IEC 60287-1-2:2023 provides a method for calculating the eddy current losses in the metallic sheaths of single-core cables arranged as a three-phase double circuit in flat formation. The sheaths are bonded at one point or are cross-bonded so that there are no significant sheath circulating currents. Where metallic sheaths are bonded at both ends there are significant circulating currents which result in a lower current-carrying capacity. A method of calculating circulating current losses for double circuits is provided in IEC 60287-1-3.
The method descibed in this document provides coefficients which are applied as corrections to the loss factors for the sheaths of one isolated three-phase circuit. These corrections are negligible for cables where the parameter m is less than approximately 0,1 (m = ω/(Rs · 107)), which corresponds to a sheath longitudinal resistance higher than 314 μΩ/m at 50 Hz.
Consequently, the method is used for most sizes of aluminium-sheathed cables, but is not required for lead-sheathed cables unless they are unusually large.
The coefficients are provided in tabular form and have been computed from fundamental formulae for sheath losses, the evaluation of which calls for expertise in computer programming which will possibly not be readily available in general commercial situations. The development of simplified formulae for some of the tabulated coefficients is under consideration.
Losses for cables in a single circuit is covered in IEC 60287-1-1.