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Cable arrangements

MG over 3 years ago

Hi all,

I have this area where I need to route a large number of single phase three core armoured cables on a tray.

Is it acceptible if I arrange the cables in a trefoil formation making sure that each trefoil group has all three phases?

0 mapj1 over 3 years ago

generally yes, it is normal to do this.
Watch for one bundle heating another, you may need more room than you think, and try to get bundles that are zero-sum with all their phase currents as far as possible. (may mean LLLN or LLL - depends on the loads, keep neutrals near the phases they relate to.)
Mike
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0 Former Community Member over 3 years ago

I am interested to hear why you think it wouldn't be ok? I have never had any issue bundling single core cables from different phases together. Obviously need to take grouping factor into account.
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0 AJJewsbury over 3 years ago

As these are single phase circuits - with presumably L, N and PE in each 3-core cable's cores - then there's no need to ensure each group is balanced across the 3 phases. Unlike were you've got single core cables, each 3-core cable is already balanced, so any grouping of those 3-core cables will be naturally balanced too.
As Mike says, beware of grouping factors - not just within each group of 3 but between groups too unless there is significant free air between groups. It might be that a single layer touching isn't so bad after all.
- Andy.
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