RCD, ELCI GFI between ABYC and ISO codes

Discussion in 'OnBoard Electronics & Controls' started by klims106, Jan 17, 2013.

  1. jonr
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    jonr Senior Member

    I agree with not needing the galvanic isolator. But a galvanic isolator will happily pass high DC voltages - it just won't pass low voltage DC that typically causes a problem.
     
  2. Landlubber
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    Landlubber Senior Member

    Thanks Ike.
     
  3. Ike
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    Ike Senior Member

    I have been sorting through all the crap I have stored on my computer and I finally found the diagram I was looking for. Here is the schematic for a boat with an isolation transformer, from ABYC E-11, electrical systems. As you can see in the diagram. on the secondary the green grounding wire is connected to the white neutral at the secondary, and there is no galvanic isolator. This is because the transformer won't pass DC inductively to the primary, as it does AC.
    The green on the primary is connected to the transformer shielding. On the secondary to the transformer casing.
    [​IMG]
     
    Last edited: Apr 29, 2013
  4. jonr
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    jonr Senior Member

    Looks good if that transformer if center tapped on the secondary side (it isn't clear, but it must be). Only thing I would consider changing is making the isolation transformer primary side also center tapped. While normally not used, this would allow plugging into a 120 VAC shore line and yet still deliver 120 VAC and 240VAC on the boat (at reduced amps). Pretty much ideal, except for 50Hz vs 60Hz issues.
     
  5. Landlubber
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    Landlubber Senior Member

  6. Mark Cat
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    Mark Cat Senior Member

    CDK is correct.

    The RCD or in the USA RCBO by CarlingTech, monitors the wiring (feeders after the device) and isolation transformer for leakage 30 mA, as well as provide traditional Circuit Breaker overcurrent protection to feeders and transformer primary.

    The RCBO can also be used as the vessel ABYC shore power main disconnect.

    A Marine isolation transformer is set up to isolate the shore and vessel grounds. It can also be provided with taps to match voltage between 230 VAC UK to 240 VAC USA systems.

    Best regards,

    Mark Cat
     
  7. Ike
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    Ike Senior Member

    There is another diagram in the ABYC E-11 standard showing it set up that way.
     
  8. jehardiman
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    jehardiman Senior Member

    Notice that the diagram in Ike's post #33 shows the shift between the "Y" wired land side and the "delta" wired vessel. The "transfer case ground connection" connects the white and green which collapses the "Y" into 2 120V phase legs (black and red) from the "ground" (white/green) phase. Note that this does not function like a land "ground"/neutral and should never be connected to the hull or the cathodic protection system. Almost all ships are wired "delta".
     
    Last edited: May 22, 2013
  9. Mark Cat
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    Mark Cat Senior Member

    jehardiman,

    FYI

    For Diagram 7 ABYC (2010 - 2011) there is a note:

    "This diagram does not illustrate a complete system"

    The ABYC drawing is single phase. The drawing is partial in that it shows just a portion of the overall electrical install. The transformer output as shown represents a separately derived AC system. Hence the connection of the grounded and grounding conductors at the transformer (source). An AC genset on-board would represent another separately derived system.

    For ABYC pleasure craft, the separately derived AC grounding system (Green or Green with Yellow stripe) is tied to the overall grounding and bonding of the vessel (also includes lightning protection). Which would include bonding to a metal hull (engine negative terminal in the drawing). The AC grounding conductor provides AC ground fault protection.

    As you have stated ships often use three phase delta for power distribution. As far as I know ABYC does not specifically provide drawings for three phase power installations.
     
  10. jehardiman
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    jehardiman Senior Member

    Almost all AC power systems, and in the USthat includes the general power grid, are 3 phase systems, an individual circut may be single, 2 phase, or 3 phase. In a "Y" system , a circut between any 2 arms of the 'Y" gives single phase 208v which is actually composed of 2 120 v waves 60 degrees out of phase. This, 240 dual or 2 phase power, is the input power shown in figure 7 (post #33 above), not a true 240v single phase. The Isolation Transformer seperates these two phases out, ( V or open delta transformer IIRC) giving 2 seperate phase, 120 v each relative to the third, ground phase.
     
    Last edited: May 22, 2013
  11. Mark Cat
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    Mark Cat Senior Member

    jehardiman,

    Yes it is possible to have 3-wire 120/208 Dock power originating from a 4-wire three phase wye system.

    However, that is not the assumption per diagram 7 from ABYC.

    From ABYC:

    "Diagram 7: Isolation Transformer System with single phase 240 Volt Input, 120/240 Volt output with boat grounded secondary. Transformer Shield Grounded on the shore. Transformer Metal Case Grounded on the Boat."

    ABYC is referencing a power distribution 3-wire + EGC single phase 120/240 transformer secondary at the dock pedestal in this example and not a 120/208 wye.
     
  12. jonr
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    jonr Senior Member

    Note that two of the input wires are labeled "ground". There is no delta, wye or 3 phases involved here.
     
  13. jehardiman
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    jehardiman Senior Member

    ACK...what a horrid way to wire a ship...but maybe not a boat. Perhaps I assume that you will need self generated 3 -phase aboard so will wire delta, not 240v dual.

    Now I see that there is a "grounded neutral" and a "grounding conductor" in the figure, so it is a 240 dual in figure 7, not a proper 3 phase. That only works with small installations (i.e. boats...not Yachts...)

    Anyway, my assumptions were wrong, possibly due to working with ships not boats.
     
  14. Mark Cat
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    Mark Cat Senior Member

    jehadiman,

    Yachts up to perhaps 70 feet (24kVA), which want maximum flexibility for shore power with many different ports of call outside of US waters, may decide to stay with a single phase setup. Easier to find single phase dock power throughout the world following either UK or US.

    To get an idea of the needed flexibility, use the Caribbean sea as area of operation, with a Charter boat possibly calling on all the major tourist ports for all countries (islands). Much easier to find single phase.

    Mark
     

  15. jehardiman
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    jehardiman Senior Member

    That is propably true, but you need to be a lot more carefull of your load balance (especially large auto-on heating/cooling loads) and noise filtering.
     
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