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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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  • 0
    broadgage:
    Chris Pearson:
    John Peckham:

    It can't be that big a block of flats at 100A a phase?


    MS01:

    My thought was this is a big block of flats 300+ which are used by students and now with lectures online mostly will be using laptops....what are peoples thoughts? 


    I did wonder: that's 1 amp per flat.


    In fact if they are centrally heated bed-sits with a shower and WC, and no kettles, etc. allowed, they probably would get by with 230 W (after diversity).




    1 amp per flat is in my view possible at times of low load, That does not mean that a 100 amp 3 phase supply is enough for 300 flats, the load could easily average 5 amps or more per flat at peak times. But an average of 1 amp at times sounds reasonable.




    We haven't been told the capacity of the supply, just that the currents in the phases are about 100 A each.


Reply
  • 0
    broadgage:
    Chris Pearson:
    John Peckham:

    It can't be that big a block of flats at 100A a phase?


    MS01:

    My thought was this is a big block of flats 300+ which are used by students and now with lectures online mostly will be using laptops....what are peoples thoughts? 


    I did wonder: that's 1 amp per flat.


    In fact if they are centrally heated bed-sits with a shower and WC, and no kettles, etc. allowed, they probably would get by with 230 W (after diversity).




    1 amp per flat is in my view possible at times of low load, That does not mean that a 100 amp 3 phase supply is enough for 300 flats, the load could easily average 5 amps or more per flat at peak times. But an average of 1 amp at times sounds reasonable.




    We haven't been told the capacity of the supply, just that the currents in the phases are about 100 A each.


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