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Cables buried directly - Grouping factor and spacing

Apostolos
Good morning.

If anyone could give me a hand with the following...
When sizing cables with a direct burial installation method, how far away from each other do cables need to be so that no grouping factor applies? Table 4C2 in BS7671 gives a derating factor of 0.8 for up to 0.5m away when there are 4 or more circuits but doesn’t state any distances exceeding 0.5m.

Should i consider that after 0.5m there is no grouping factor for example???

Thanks!
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    In general burial is a funny thing, as the thermal properties of the backfill sand soil or whatever, are very dependent on local moisture levels and the proximity to the surface, and real performance can actually be very variable. Assuming that cable depth is ~ half metre or so then any neighbour cable that is further than the surface is not so significant as the surface is the dominant cooling surface (but of course the cables may be deeper...).

    The model of use a constant grouping factor and up to some distance and then switching it off suddenly is a bit of a simplification. It also does not consider the long term drying out of the ground around the cables altering the behaviour.
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    In general burial is a funny thing, as the thermal properties of the backfill sand soil or whatever, are very dependent on local moisture levels and the proximity to the surface, and real performance can actually be very variable. Assuming that cable depth is ~ half metre or so then any neighbour cable that is further than the surface is not so significant as the surface is the dominant cooling surface (but of course the cables may be deeper...).

    The model of use a constant grouping factor and up to some distance and then switching it off suddenly is a bit of a simplification. It also does not consider the long term drying out of the ground around the cables altering the behaviour.
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