Transformer on a Floating Barge

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DutchRiviera

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Hello. I have an unusual situation I was wondering if I can pick your minds about. I am designing the electrical system for an emergency boat launch/floating barge. The floating barge is accessed via a partially floating bridge that pivots with the tide level. I am running 480V 3ph (about 500') to the barge and stepping down to 240V 1ph to handle misc. 120V loads. My question is this: How do I establish a GEC for the transformer on the floating barge?

Any help on this matter is greatly appreciated. I thank you in advance.

Dutch
 
Hello and welcome to the forum.

I can't say that I've ever dealt with a situation like that but it seems like article 553 & 555 are the most relevant in the NFPA70. Now, your description is pretty short, but from what I imagine you have a permanent raceway (may not be the correct terminology) that allows the phase conductors to feed the floating barge. I would think that you need to run a EGC back to the mainland using similar means and connect it to the grounding system there. As far as the transformer, I think you need to connect the EGC to the body as well as all the metallic structs/supports. The neutral conductor (assuming 4w system) will need to be ran back to the mainland similarly and then treated as a regular connection after that per NEC. I would think you can't establish a GEC at the transformer installed on the floating platform... on the same note, why not install the transformer on the land? Please note that the above is only my speculation and there are probably major flaws and inadequecies in the above statements due to my inexperience with this type of installation and lack of information/details - but for what it's worth that's my 2 cents.
 
553.8(D) Grounding Electrode Conductor Connection.

The grounding terminal in the service equipment shall be grounded by connection through an insulated grounding electrode conductor to a grounding electrode on shore.



I would say the same could be done for the transformer grounding.
 
skeshesh said:
Hello and welcome to the forum.

I can't say that I've ever dealt with a situation like that but it seems like article 553 & 555 are the most relevant in the NFPA70. Now, your description is pretty short, but from what I imagine you have a permanent raceway (may not be the correct terminology) that allows the phase conductors to feed the floating barge. I would think that you need to run a EGC back to the mainland using similar means and connect it to the grounding system there. As far as the transformer, I think you need to connect the EGC to the body as well as all the metallic structs/supports. The neutral conductor (assuming 4w system) will need to be ran back to the mainland similarly and then treated as a regular connection after that per NEC. I would think you can't establish a GEC at the transformer installed on the floating platform... on the same note, why not install the transformer on the land? Please note that the above is only my speculation and there are probably major flaws and inadequecies in the above statements due to my inexperience with this type of installation and lack of information/details - but for what it's worth that's my 2 cents.
Click to expand...

Thanks for the response.

Installing the transformer on land would seem like a good idea, except the loads I'm feeding would be nearly 600' away and that seems pretty far for 120/240V, 1ph.

The current design is bringing 480V, 3ph from a power pole down to a meter and main safety switch (which is where I establish the GEC on the 480V side), then running a feeder (Type W) underground and then close to the underside of the bridge to the 480V panelboard on the floating barge. From there I go to a transformer and step down to 120/240V, 1ph, which feeds the other panelboard. Somehow I need to establish the GEC for the 240V side on a floating barge.

I'm still scratching my head...
 
Well i agree its not in the NEC its in the IEEE STD 45-2008 recommended practice for shipboard electric energy & power .

And the US Coast guard will inspect your installation not your local county electrical inspector.

Ship to shore power or what the navy calls cold iron connection http://i611.photobucket.com/albums/tt195/stringking/navycoldironing.jpg

Your hull is your point of ground

PM me if you like ive worked shore power here in florida for disney .
 
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