Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

3x230V grids without neutral -- What countries use it?

  1. Jan 9, 2017 #1
    Does anybody here happen to know which countries have 3x230V grids without neutral. I know that this exists in some areas in France and Belgium. Was told Norway as well, not sure? Any other?

    Thanks
     
  2. jcsd
  3. Jan 10, 2017 #2

    Bandit127

    User Avatar
    Gold Member

    Try a google search for:
    3 phase supply voltage by country
     
  4. Jan 10, 2017 #3

    Svein

    User Avatar
    Science Advisor

    Norway is correct, but the power companies are starting to introduce 4-lead distribution, also called 400V distribution (the classic 3x230V is a delta connection, the 4-lead is a star distribution).
     
  5. Jan 10, 2017 #4
    I presume you have RCDs in Norway. Does that mean that 1 leg is connected to ground?
     
  6. Jan 11, 2017 #5

    Svein

    User Avatar
    Science Advisor

    No. Check out https://en.wikipedia.org/wiki/Three-phase_electric_power. The article contains a drawing:
    220px-The_basic_3-phase_configurations.svg.png
    And a short notice: "There are two basic three-phase configurations: wye (Y) and delta (Δ). As shown in the diagram, a delta configuration requires only 3 wires for transmission but a wye (star) configuration may utilise a fourth wire. The fourth wire, if present, is provided as a neutral and is normally grounded. The "3-wire" and "4-wire" designations do not count the ground wire used above many transmission lines, which is solely for fault protection and does not carry current under non-fault conditions."
     
  7. Jan 11, 2017 #6
    That surprises me. Seems extremely dangerous to me as these lines float with respect to ground, meaning they can be at any potential including a leak, capacitive or inductive coupling from a 10kV primary for example. Furthermore RCDs are no longer functional in such configuration.
     
  8. Jan 11, 2017 #7

    Svein

    User Avatar
    Science Advisor

    1. The center of the delta is grounded at the local supply transformer (5kV-230V).
    2. Every house must provide a local safety ground connection. It is not connected to any of the supply wires.
    3. Both wires are considered "live".
    4. I do not know exactly what an RCD does, but from about the year 2000, every fuse in the fuse cabinet must include a Ground Fault Interrupter circuit. A GFCI works by measuring the current leaving one side of a power source (the so-called "live" or "hot wire"), and comparing it to current returning on the other (the "neutral" side). (cited from https://simple.wikipedia.org/wiki/GFCI). Thus, the potential on the wires relative to ground is completely irrelevant.
     
  9. Jan 11, 2017 #8
    There's some "inconsistencies" here.

    1. Delta windings don't have a center, that's the nature of the problem
    2. That's the case in most parts of the world but has only meaning if the supply side is grounded as well. A return path via the earth must exist for earthing to be functional
    3. Understandably
    4. Aaah, you make use of a GFCI. Difference with a RCD is that the latter trips in case of a ground failure. A GFCI only tells you the problem is there. Someone has to come and fix it ASAP. It's called an IT-system. That also means that high impedance grounding must exist at the supply side either via one leg of the transformer or an artificial neutral point.

    Interesting to know. Finland is probably is probably the only part of the world where this is used in the public sphere other than hospitals. Got to visit that place :-)
     
  10. Jan 11, 2017 #9

    Svein

    User Avatar
    Science Advisor

    Yes, but the supply transformers do not have to be in a delta configuration in order to supply three-phase delta. They may just as well be in a wye configuration and then it is easy to ground the center.
    Well, it trips when the imbalance is >15mA (or 10mA, I do not recollect).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: 3x230V grids without neutral -- What countries use it?
Loading...