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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
    Sparkingchip:

    . . .

    What is frequency?



    Alternating current (ac) frequency is the number of cycles per second in an ac sine wave. Frequency is the rate at which current changes direction per second.

    . . .

    So what happens if there’s more than frequency in the same conductor, does the tester register the “dominant” frequency or a mish mash of them.


    Andy B.




    I don't like this as a definition of frequency. For a start, a frequency of 50 Hz involves 100 changes of direction per second. Also, if you take an open circuit, you can still talk about a supply frequency even though no current is flowing.


    Realistically, frequency is the number of times per second at which the electro motive force goes through a complete cycle of positive and negative direction.


    And as you say, Andy, there can be more than one frequency in the conductor, as this fascinating discussion has revealed. It is quite possible, with heavy harmonics, for a doubling of frequency to occur. Hence 200 changes of direction of current per second with an applied e.m.f. of 50 Hz.


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  • 0
    Sparkingchip:

    . . .

    What is frequency?



    Alternating current (ac) frequency is the number of cycles per second in an ac sine wave. Frequency is the rate at which current changes direction per second.

    . . .

    So what happens if there’s more than frequency in the same conductor, does the tester register the “dominant” frequency or a mish mash of them.


    Andy B.




    I don't like this as a definition of frequency. For a start, a frequency of 50 Hz involves 100 changes of direction per second. Also, if you take an open circuit, you can still talk about a supply frequency even though no current is flowing.


    Realistically, frequency is the number of times per second at which the electro motive force goes through a complete cycle of positive and negative direction.


    And as you say, Andy, there can be more than one frequency in the conductor, as this fascinating discussion has revealed. It is quite possible, with heavy harmonics, for a doubling of frequency to occur. Hence 200 changes of direction of current per second with an applied e.m.f. of 50 Hz.


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