SMA long distance Grid tie [RE-wrenches]

[William Korthof]

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I've done these long distance installations several ways. I would
definitely avoid using transformers and changing voltage unless
it really becomes necessary.

There are a number of good online voltage drop calculators...ex:

http://www.csgnetwork.com/voltagedropcalc.html
http://www.electrician.com/vd_calculator.html
http://www.elec-toolbox.com/calculators/voltdrop.htm

For 50 amps at 240 Vac, 2/0 copper or 4/0 aluminum is 2% drop.

For 9 amps at 240 Vac, 4 awg is 1.9%

Wire sizing is a little better if you make the long distance run on
the DC side (higher voltage). You get to work with parallel wires
(1-2 pairs per inverter)... the risk of the inverters tripping off line
(utility overvoltage or frequency error) also goes down. The Vdrop
on the DC side is easiliy handled by the MPPT. Remember that
solar panels have very high resistance; typically 25-30%, so an
extra 2-3% for the connection wiring is trivial.

/wk

At 02:27 AM 9/3/04 -0400, you wrote:

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>Currently have an installation with 6 pole mount arrays, each having a 
>dedicated SB2500. The arrays are roughly 500' from a small building, which 
>the customer had built to house his generator, the inverters and 600A 
>service before distributing power to the rest of the property.
>
>I have spoken with SMA, which has been most helpful. Recommending that I 
>place the inverters at the modules- then string them together, combine 
>them into an ac panel, then use a transformer to step up the voltage for 
>the 500' run, then use another transformer to step it back down before 
>going into the building. Using some type of photo control to turn the 
>transformers off at night, to cut the wasted power consumption also. This 
>would allow the use of #2 for the 500' run.
>
>I investigated the transformer idea and have looked at the companies web 
>sites suggested by SMA . No solid solution yet.
>
>Has anyone on the list with real time experience with installing multiple 
>grid tie inverters using the same technique? What has your experience 
>been? What would you have done different and why?
>
>All input is appreciated.
>
>Best Regards,
>
>Dan Whigham
>www.scsolar.com
>Phone 803-802-5522
>Fax     803-233-1750
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