In Annex D3(a), the neutrals complicate feeder sizing because we cannot assume the load is evenly distributed. Let's see just how much more complicated this becomes.
After that first long paragraph, Annex D3(a) provides a summary of the loads. The first one listed is discharge lighting. This type of load has high nonlinear content, so there's substantial current flowing through the neutral. That means you must consider the neutral to be a current-carrying conductor.
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