For single-core cable circuits with sheaths solidly bonded at both ends and possibly at intermediate points, the circulating currents and the resulting losses increase as the spacing increases, and it is advisable to use as close a spacing as possible. The optimum spacing is achieved by considering both losses and mutual heating between cables.
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The IEC 60287-1-1 chapter 2.3.4 has recommendations for the calculation of sheath circulating current losses when it is not possible to install cables with a constant value of spacing over the length of one electrical section.
The recommendations give values for loss factors which apply to the whole of a section, but the appropriate values of conductor resistance and external thermal resistance must be calculated on the basis of the closest cable spacing at any place along the section. The optimum spacing is achieved by considering both losses and mutual heating between cables.
Spacing variation for double-sided bonded single-core cable systems acc. to IEC 60287-1-1, chap. 2.3.4 has been implemented in Cableizer. You have the following possibilities based on the three IEC recommendations:
This variation of spacing has only an influence on the screen/sheath losses and does not consider higher or lower mutual heating due to changing distances between cables which has a larger impact on ratings. That is why we limited the input of variation to +/- 50% of center - center spacing.