Components for middle tension grid conection

 Hello,

Can some one tell me all the components necessary for a photovoltaic
(250 kW) grid connection in mid tension?

What you guys think it is the best photovoltaic module in the market?

Many thanks,
Ricardo

 
What is mid(dle) tension?

What the "best" panel is will depend on your criteria.

 
<William P.N. Smith> wrote in message

Off the top of my head.
Low tension.
0 to around 480v one two or three phase.
What is delivered to the normal home or company.

Mid tension.
1kv to around 14kv, normally one, or three phase.
The normal level for local distribution.
Some areas of the south run up to 28KV+ for local distribution.

High tension
48KV to 2MV+ for regional to long distance transmission of power.

He is wanting to know what equipment
is available for feeding power to the grid,
at the local distribution voltage.
(ie) an inverter with a 7.2KV output,
or what ever the grid voltage is around his location..
At the 250KW level, it would be the preferred method..

 N9WOS wrote:

The large systems that I've seen described seem to consist of
a standardized small system, say 2 or 3 kilowatts, with a single
240V inverter and they simply multiply this many times. All these
feed back into standard grid step-down (or up) transformer(s).

Anthony

 

I looked for information on distribution voltage grid tie inverters,
but I didn't have any luck.

It surprises me that they are not a regular item.
I would say that one company will get a clue and make one,
when larger installations become more common.

I would ask your utility company and see if they could point you
to anyone that makes such a beast, or could custom build one for you.
It would reduce the PV to grid losses by removing a transformer stage.
(ie) instead of DC to Low voltage AC to 7.2KV
You would just have DC to 7.2KV

But without that, other choice would be obvious.

The highest PV and intermediate AC voltage you can get.
Something like one these units, with a 300 to 600+ volt dc input,
and a 480Vac, one or three phase output.

http://www.inverpower.com/products/alten/50%20kW%20PV%20PCS%20Model%20Specifications%20Jun%202804.pdf

http://www.cisolar.com/catLargInv.html


http://shop.altenergystore.com/XQ/ASP/ic.XANPV15-480KIT/QX/itemdesc.htm

http://www.electronicproducts.com/ShowPage.asp?Section130&PRIMID=&FileName=XHLAP08.jul2004.html

http://www.xantrex.com/web/id/1102/docserve.asp

One, two, three, or more inverters connected to one transformer.
The transformer being a 200kw-250kw 480Vac 3 Phase pad mount transformer.
The 480Vac intermediate voltage would reduce the wiring losses between
the inverter and the transformer as compared to 240Vac.
And a 3phase inverter with transformer would more evenly feed the grid.

Or you could have two or more pad mount transformers
that is being driven by separate inverters,
if you are going to have the inverters separated by a large distance.

(ie) instead of long 480V runs to connect five 50KW inverters,
that are separated by 300 feet..
You could use five 50KW transformers, one at each inverter.
And then send the power to the grid connection point at distribution
voltages.
Which would result in less power loss.

One 250KW transformer is more efficient than five 50KW transformers.
But one 250KW transformer being driven by a 300 foot piece of cable
at 480V, is less efficient than five 50KW transformers being driven by 10
foot long cables.

And try to get an array voltage that is on the higher end of the limit.
It will complicate the DC protection, but it will improve efficiency.
(less copper loss)
As with anything, there is always trade offs.

Just take my opinion as a suggestion.
I don't claim to speak with any experience in that type of equipment.
I am just a by stander that thinks he has a clue as to what you are wanting.
If I don't, then just ignor me.