current on the neutral

[kendor]

what is wrong with "balancing the single phase load across all 3 phases?

for sake of argument 300 lights, 100 on each phase (and obviously all connecting to neutral) = balanced load (almost)

The word "almost" summed up exactly what i was saying! Although in your argument what load would the neutral be seeing? 300 lights of course! People seem to be forgetting how a clampmeter is used, you don't include phase AND neutral to get a reading you measure each core seperately including the neutral and therefore the author who from the sounds of it was using the clampmeter correctly saw current flow.
To add to the variables what tolerances do manufacturers work to in creating electrical equipment whether motors, lamps, pc's whatever, no two items will have identical specs, if for instance you need closely matching equipment /components then you normally pay through the teeth for it say for laboratory specifications, but even then fine tuning needs to be incorporated as you still get slight variations.

So say take a hypothetical laboratory installation with finely tuned equipment, each piece of apparatus will show almost negligible "unbalance" but multiply that a hundred fold what would you see at the supply to the installation? exactly!

 

[Big_Spark]

what is wrong with "balancing the single phase load across all 3 phases?

for sake of argument 300 lights, 100 on each phase (and obviously all connecting to neutral) = balanced load (almost)

Can't be done, not economically at any rate.

Designing such a system would be a logistical nightmare, every piece of cable connecting light fittings would need to be specific, predermined lengths to ensure all cable resistances were identical to ensure that all volt drops were equal to within 100ths of a volt. Nominal voltage regulators would be required to be fitted to each circuit to ensure that the voltage did not fluctuate above or below a predermined level.

Every switch and every piece of equipment would need to be manufactured to the kind of tolerances required by NASA.

Who would pick up the bill? At this level, even a house rewire would cost 100's of 1000's of pounds.