On 15 Aug 2017 at 8:00, James Cameron wrote:

> Brett, thanks.  Yes, AS/NZS 5033 will apply.  I'll see if I can bring
> the distance down below 50m by dropping three trees instead of nine.
> AS/NZS 5033:2014 is alleged to also require maximum voltage drop of
> 3%, and maximum Voc of 600V unless access restriction is added.
>
> https://www.gses.com.au/wp-content/uploads/2016/03/5033-2014-Changes.pdf
>
> (Access to standards is an irritation for me; used to be able to get
> at them through public library, but the library lost access.  My own
> business isn't yet able to justify the expense of formal access;
> mostly I'm doing software and firmware.)

Access to standards is a pain here too, but being the holder of an electric=
al worker=20
licence does get you on-line access to a number of standards, which is usef=
ul.

> 1.  longer cable means larger voltage drop, that adding a panel brings
> the total power above the maximum array power of the inverter charger.
> But if that is the case then it should be accepted because of the
> voltage drop. And the input will be MPPT anyway.

The complete sentence in AS/NZS 5033:2014 is "It is reccommended that under=
=20
maximum load conditions the voltage drop from the most remote PV module in =
the=20
array to the input of the PCE (inverter) should not exceed 3% of the Vmp vo=
ltage (at=20
STC) for LV PV arrays".

So given the voltage drop is just a "reccomendation", I'd imagine it could =
be ok to=20
exceed it, if you have a good techincal reason for doing so and providing e=
verything=20
else remains satisfactory, eg. for one thing, temperature rise in cable.

Also, it seems to me the difference between Vmp max load and Vmp STC would =
not=20
be nearly as much as between say Vmp max load and Voc (no-load), so the 3%=
=20
drop should be much easier to acheive. Or else I'm reading it wrong and con=
fusing=20
myself.

Also also, (sorry if you already know) it seems quite common and acceptable=
 to use=20
"under-sized" inverters... eg. say 6kW of panels on a 5kW inverter. Peak ge=
neration=20
is only limited for a short time each day/some days, eg around mid-day on a=
 fine=20
day in mid-summer, as the inverter will (should) limit the output to 5kW so=
=20
everything stays within spec. The rest of the time below 5kW you still get =
the=20
advantage of the extra panels.

I don't actually have any direct experience with DC PV arrays, I only have =
a 5kW AC=20
micro-inverter system myself. Over the last 18 months or so apparently I've=
 "saved"=20
354 trees... living in town I have no idea where I'm going to put them ;-)


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