Harmonics in the Neutral

[Stanthorpe]

We have a lighting installation that has Harmonics in the main neutral conductor at 120%, minimal on the phases
The temp is at 110deg Celsius on the neutral, phases 40 deg
80Amps on the Neutral
Phases 200Amps each phase
Load is 320 LED drivers single phase, balanced across each phase
The supply transformer has been cleared of causing the harmonics by running the load on a generator
when the load was un balanced on the three phases the Harmonics dropped to 63%, temp dropped to 40deg celsius
Which is contrary to advice received for the industry
help

 

[stevenal]

Triplen harmonics add in the neutral. It is common to upsize the neutral for non-linear loads.