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Thread: Harmonic issues

  1. #1
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    Harmonic issues


    PUT SOME NEW CAPACITORS IN MY PLANT AND RECENTLY BLEW ONE UP. THE REASON WHY WE REPLACED THEM IS TO GET RID OF THE PCBs IN THE OLD ONES WHICH WHERE NOT HOOKED UP WHY? IT'S AN OLD BUILDING THESE CAPACITORS WHERE DISCONNECTED BEFORE MY TIME I GOT HERE 10 YEARS AGO. BEING TOLD BY THE MANUFACTURER THAT THE REASON WHY WE BLEW ONE UP IS DUE TO A HARMONIC ISSUE. COULD SOMEONE TELL ME WHAT IS THE BEST WAY TO CHECK TO SEE IF THERE IS INFACT A HARMONIC ISSUE. THANX FOR YOUR HELP.



  2. #2
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    Re: Harmonic issues

    source from wikipedia
    http://www.electrical-installation.o...uate_harmonics
    Basic solutions to attenuate harmonics





    To limit the propagation of harmonics in the distribution network, different solutions are available and should be taken into account particularly when designing a new installation.
    Position the non-linear loads upstream in the system

    Overall harmonic disturbances increase as the short-circuit power decreases.
    All economic considerations aside, it is preferable to connect the non-linear loads as far upstream as possible (seeFig. M16).




    Fig. M16: Non-linear loads positioned as far upstream as possible (recommended layout)
    Group the non-linear loads =

    When preparing the single-line diagram, the non-linear devices should be separated from the others (see Fig. M17). The two groups of devices should be supplied by different sets of busbars.


    Fig. M17: Grouping of non-linear loads and connection as far upstream as possible (recommended layout)

    Create separate sources

    In attempting to limit harmonics, an additional improvement can be obtained by creating a source via a separate transformer as indicated in the Figure M18.
    The disadvantage is the increase in the cost of the installation.


    Fig. M18: Supply of non-linear loads via a separate transformer
    Transformers with special connections

    Different transformer connections can eliminate certain harmonic orders, as indicated in the examples below:
    • A Dyd connection suppresses 5th and 7th harmonics (see Fig. M19)
    • A Dy connection suppresses the 3rd harmonic
    • A DZ 5 connection suppresses the 5th harmonic
    Last edited by install monkey; 12-04-2012 at 08:48 PM. Reason: copied page didnt display pics

  3. #3
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    Re: Harmonic issues

    http://www.omicron-lab.com/isaq-100/...FYsntAodkiOrEA
    for measuring and monitering power,freqency

  4. #4
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    Re: Harmonic issues

    Hi Nanuuk.
    are you commenting on power factor correction capacitors, if that is the case, I have had a few really old generation types have melt downs and burn out. (messy result ). Suggest replacing the whole system with new tech system

  5. #5
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    Re: Harmonic issues

    To check if there's a harmonic issue, you need to measure the supply and make a Fournier analysis on the measured values.http://www.dee.hcmut.edu.vn/vn/bomon...s-harmonic.pdf
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  6. #6
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    Re: Harmonic issues

    Rent an instrument to register power quality, there must be many around you.

    If you have harmonics strong enough to burn a capacitor, all your electronic equipment is in danger too.

    So you need a good diagnostic but I would also check other causes like the capacitor not being the correct voltage, compressors taking longer to start (if they are hooked to a compressor), uncertified capacitor, etc.

  7. #7
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    Re: Harmonic issues

    I remembered that 3rd harmonics add up in the neutral wire of a three phase system, and this may cause measurable voltage drops.

    So if you have neutral try to check its voltage to (protective) groud, if this is in the order of 1V or higher you may either have this problem or high resistance to earth, none of which are good.

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