[RE-wrenches] PV testing

[Chris Mason]

Just a note: The PV150 does insulation testing as part of the series of
"one-button" tests. They include:

   - Earth / ground continuity
   - Open circuit voltage
   - Short circuit current
   - Insulation resistance
   - DC operating power
   - Operational current
   - Polarity
   - Earth test lead null

The American solar industry really should start implementing the IEC 62446
standard on system commissioning and testing standard for all PV
installations.
http://www.seawardsolar.com/downloads/Standardizing-PV-System-Documentation_and_Verification.pdf

On Mon, Oct 5, 2015 at 11:08 AM, Bill Hoffer <sunengser at gmail.com> wrote:

> Bill
>
> Performance verification would be your first test that can be done with 2
> clamp on meters ( idealy two Power meters like the Seaward Clamp Power
> Meter ) , ie testing under load knowing the irradiance and cell
> temperatures and measuring watts in and watts out of the inverter.  With
> that data you should be able to tell if the array is at maximum power point
> and/or if the Inverter is operating within spec.  You should account for
> irradiance, cell temperature and Light Induced Power degradation ( 1% loss
> per year unless module manufacturer warranty defines it differently),
> voltage drop soiling etc...
>
> IMHO Curve tracers are a huge investment in money and time to learn how to
> get meaningful information out of them.  Also the 3 choices currently
> available each have limitations that make it hard to decide which is the
> best solution. That would be my last investment on the list of test tools.
> Better to invest in a Insulation Resistance Tester and then something like
> the PV150 tester ( which can also do DC Power measurements).
>
> Bill
>
> On Sun, Oct 4, 2015 at 6:56 PM, frenergy <frenergy at psln.com> wrote:
>
>> Wrenches,
>>
>>        As time passeth, we're bumping more into older PVs/arrays that
>> have questionable outputs.  After minimizing the variables (dust, temps,
>> sun angle, wiring, expected deterioration with age, etc) and still coming
>> up with low numbers.  Testing individual PVs' Voc and Isc don't seem to
>> tell the whole story as they often look good.
>>
>>        Would not a definitive test be to wire a suspect PV to an
>> inexpensive mppt CC (oxymoron?) and then to an orphaned battery.  The
>> battery would have to have a mondo (surplus) rheostat paralleled to it to
>> maintain a steady voltage during the test.  With appropriate metering in
>> place, you would then have Vmmp and Immp as the rheostat is tweaked to hold
>> a steady batt voltage and the CC finds the knee.
>>
>>        Help me here.  I know its a little spendy to cobble up but the
>> value of nailing an offender might be worth it.  Am I missing something?
>> Is it common for inverters to fall off in output gradually?
>>
>> Bill
>> Feather River Solar Electric
>>
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>
> --
> William Hoffer
> 161 SE Fourth Ave
> P.O. Box 1823
> White Salmon, WA 98672-1823
> sunengser at gmail.com <bhoffer at sunergyengineeringservices.com>
>
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-- 
Chris Mason
NABCEP Certified Solar PV Installer™
Solar Design Engineer
Generac Generators Industrial technician

www.cometsolar.com <http://www.cometenergysystems.com>
264.235.5670
869.662.5670
Skype: netconcepts
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