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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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    I don't think anyone tries to balance three single phase loads.


    The important issue is that, without harmonics , the neutral current cannot be larger than the largest single phase current. Any additional loads on a different phase reduce the neutral current so the neutral does not need to be larger than the phase conductors.


    Now start to consider harmonics and this logic goes out the window as, mathematically, the neutral current can be twice the largest phase current.
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  • 0
    I don't think anyone tries to balance three single phase loads.


    The important issue is that, without harmonics , the neutral current cannot be larger than the largest single phase current. Any additional loads on a different phase reduce the neutral current so the neutral does not need to be larger than the phase conductors.


    Now start to consider harmonics and this logic goes out the window as, mathematically, the neutral current can be twice the largest phase current.
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