Results 1 to 7 of 7

Thread: Convert from Phase-to-Phase to Phase-to-Neutral for a 3-Phase 3-Wire unbalanced syst

  1. #1
    Join Date
    Apr 2017
    Location
    UK
    Posts
    6

    Convert from Phase-to-Phase to Phase-to-Neutral for a 3-Phase 3-Wire unbalanced syst

    Hi all,

    As the title suggests I am trying to understand what is involved in converting from P-P to P-n values.
    More specifically I am trying to understand what the process for doing this is, if I had the raw waveform data from two VTs (assuming middle phase is grounded).
    i.e Is there a simple vector math I can perform on each measured sample?
    Or maybe a more complex trigonometric(/phasor diagram) based solution to get from P-P to P-n.

    Please state assumption made and remember its a 3-phase, 3-wire unbalanced solidly ground system.

    I also trying to understand what functions other than power metering (eg protection?) I could perform on the obtained signals/variables.

    If you have links, manuals, or books to point me to that would be great.

    Thanks
    Alex
    Attached Images Attached Images  

  2. #2
    Join Date
    Apr 2017
    Location
    UK
    Posts
    6
    Correction:

    *(assuming middle phase input into meter is grounded).

  3. #3
    Join Date
    Apr 2008
    Location
    Ann Arbor, Michigan
    Posts
    6,843
    190208-0950 EST

    I believe your question is about measurement of three phase power or energy with two single phase watt or watt-hour meters. Your post title did not seem to imply this, but text and drawing did. No wire needs to be earthed or called ground for this measurement.


    See http://forums.mikeholt.com/showthread.php?t=189230



    .

  4. #4
    Join Date
    Jan 2016
    Location
    PA
    Posts
    5,481
    you want a ph-n voltage on a system with no n?
    why?
    The difference between genius and stupidity is that genius has its limits.

  5. #5
    Join Date
    Apr 2017
    Location
    UK
    Posts
    6
    Apologies for not replying earlier.
    I didn't see any notifications in my inbox.

    I am trying to understand the wiring diagram and internal (software) operation of a power meter for three phase, 3-wire systems.
    My understanding is that while 3-ph, 3-wire (11kV, solidly ground system) do not have a neutral, the transducers (delta-wye) that step down the voltages are in fact grounded and measuring with respect to ground.
    Does this not make the inputs into the power meter (/ADC) phase-to-ground?
    My best guess then, is that the power meter will then internally convert the phase-to-ground to phase-to-phase? Which is why I mention the p-n to p-p conversion.

    Also trying to understand the difference between Aaron method for measuring power using two power meters as gar mentioned above AND a similar but different method where a wye-wye VT has secondary L2 grounded while having a second set of secondary VTs connected as open delta. For example in power generation like one mentioned here:
    http://www.eng-tips.com/viewthread.cfm?qid=200371

    Thanks and regards
    Alex

  6. #6
    Join Date
    Sep 2008
    Location
    UK
    Posts
    11,376
    Quote Originally Posted by Ingenieur View Post
    you want a ph-n voltage on a system with no n?
    why?
    A curious question indeed.
    Si hoc legere scis nimium eruditionis habes.

  7. #7
    Join Date
    Nov 2007
    Posts
    835
    Quote Originally Posted by Besoeker View Post
    A curious question indeed.
    Maybe something went awfully wrong when typing things!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •