[RE-wrenches] Commercial design predicament

[penobscotsolar at midmaine.com]

Thanks for the reply guys. Yes, the utility is saying that it will be at
the customers cost run three phase that mile or so. It is prohibitively
expensive with the clients business plan. My thought is that multiple
smaller, single ph inverters could be used to then tie into a transformer
which would up the single phase voltage to 7200 volts. This would be a
current of less than 80 amps. The utility says the existing (single phase)
lines out to the site can handle the current of a 500 kW solar farm. I
will need to find the proper transformer(s), of course, if they exist.
Using multiple smaller inverters would likely make the tie in to that
transformer easier (or at least smaller wire sizing....)
Just my thoughts. I haven't given up yet....

Daryl


> Daryl,
> I don't think there's a practical way to make this work either. If you
> were
> adding a 500kW load to that site, the utility would gladly bring out a
> three-phase transmission line with an appropriate transformer.
> Unfortunately, for a solar farm, the utility probably wouldn't be willing
> to do that for free and would require three-phase service-- even though
> it's technically possible with a big batch of 10kW 1P inverters.
> Unfortunately, running the line that mile out to you could be a few
> hundred
> thousand dollars. It's worth checking with the utility, but I'd guess
> you'd
> have to pay for the extra mile of 3P distribution line.
>
> Dave
>
>
> On Fri, Dec 14, 2012 at 10:12 AM, <penobscotsolar at midmaine.com> wrote:
>
>> Hello fellow wrenches,
>>    I am hoping someone here has come across this before and might have a
>> suggestion or two for us. I have a client who has a large piece of land
>> and the financing for a 500 kw solar "farm" in Maine. The predicament I
>> am in is that the closest three phase primary is more than a mile away.
>> The existing single phase, 7200 volt lines to the three phase portion
>> of the grid could easily handle the -80 amps extra load coming onto it
>> from the central inverters, it is just that I cannot find, anywhere, a
>> practical way to make this work, that is, converting the three phase
>> output of the central inverter(s)(480v) to the requirement for the grid
>> (7200 v single phase). Any ideas?? Suggestions?
>>
>> Thank you,
>> Daryl DeJoy
>> NABCEP Certified PV installer
>> Penobscot Solar Design
>>
>>
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