I have some commitments that are :
– Where there’s harmonics in a network, the phases’ currents will be increased accordingly, and the Neutral current will be composed of :
– The Vectorial Sum of the 3 phases’ currents.
– The Sum of the 3rd harmonics that means “ 3, 9, 15, 21, … ”
So, the Neutral current will be equal or bigger than the phase current depending on the values of the 3rd harmonics, but when we haven’t the Neutral current will be only the Vectorial sum of 3 phases’ currents that’s small.
– When we have harmonics in a network, and depending on the harmonics’ values and types, we will decide the sizes of the Neutral lines, but not using always “ Double-size ” of these lines.
– When we do the study of any project, as we have all necessary information about the loads, we should know if there are harmonics or not, if yes, what the kind of them to find the best solution at the beginning. Either for Phases or Neutral sizes cables.
– As recommendations, You said about the Neutral lines “ …. or separate neutrals for each phase ”, please explain how you can separate the neutral if you have a machine generating harmonics that should be supplied by “ 3 P + N ” ???? We can use your solution only for Lighting Circuits supplied by “ 3 P + N ” but not for other Single Phase Circuits. Normally, we supply single each circuit by Phase + Neutral, and accordingly the IEC… standard it’s not permitted to use the same neutral for many Single Phase Circuits.