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High 3rd harmonic on the neutral

MS01
Afternoon,

I was wondering if anyone has nay experiences of having issues with high 3rd harmonic currents on the neutral on high-rised residential schemes? I appreciate  non-linear single phase loads will impact the 3rd harmonic and even on a balanced system harmonics are an issue but we are measuring it at 300% but I can’t think why this may be the case on a residential building.

Does anyone have any ideas?



M
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    With a three phase delta connection only one phase is live at a time and the return path is via the other phase conductors, so no neutral connection is required at all, because the load is connected across the phases.


    Edit- with a star connection neutral current will pass to the other phases at the star?


    With single phase the return path is always via the neutral and cannot be returned via the other phases.


    So how can you cancel single phase return currents down to zero in the neutral conductor?


    Can someone sketch out the layout of a building installation such as this with a X to mark the point where the neutral currents cancel each other out?


    Andy Betteridge
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  • 0
    With a three phase delta connection only one phase is live at a time and the return path is via the other phase conductors, so no neutral connection is required at all, because the load is connected across the phases.


    Edit- with a star connection neutral current will pass to the other phases at the star?


    With single phase the return path is always via the neutral and cannot be returned via the other phases.


    So how can you cancel single phase return currents down to zero in the neutral conductor?


    Can someone sketch out the layout of a building installation such as this with a X to mark the point where the neutral currents cancel each other out?


    Andy Betteridge
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