Tip:
Highlight text to annotate it
X
Seen one of these before?
Hello, my name is Mick and I am going to step you through the requirements for testing and
commissioning a grid-connected Solar PV system after you have installed it.
Did you know that according to the Wiring Rules, all electrical installations must be
tested prior to being commissioned?
This applies to every electrical installation including solar PV.
The Australian Standard for the Installation of PV arrays (5033) lists the specific tests
for commissioning PV installations. Installers should also refer to the Clean Energy Council's
Install and Supervise Guidelines that are available on the solar accreditation website.
The guidelines provide a sample PV array commissioning checklist for grid-connected installations.
You must complete a testing and commissioning sheet and provide a copy to the customer.
So let's get started. You've now completed the wiring and are now ready to test the installation
before signing it off and handing it over to the customer. It is best to start at the
array and systematically work towards the inverter and finally the switchboard.
[♪ Music ♪]
And a little warning before you start, many PV strings operate at voltages in the hundred
of volts and can cause death by electrocution. So use safe work practices and test before
you touch.
Before getting on the roof, make sure the DC array isolator at the inverter is locked
off and cables are disconnected.
First off, let's check the continuity and resistance of all earth connections and the
module frames with an IR tester NOT a multimeter. A multimeter is not accurate enough. And remember
to zero the meter first when using a trailing lead. 3000 states that the resistance of any
equipotential bonding conductor shall be not more than 0.5 Ω.
Record the results.
Now let's see if you have connected all the modules and not missed any of them. This is
best done by measuring a single module then doing the maths and multiplying by the number
of modules in the string, and finally testing the whole string to compare the voltage reading.
While checking the continuity and voltage of each string, also check the polarity and
record that result as well. Then short out the string and measure the short circuit current.
Now before you get off the roof, check that all the strings, and isolators are connected
and do a final polarity check at the isolator before putting on the cover.
Turn the DC isolator on before going down to the inverter.
Now, with the array testing done, you can test the wiring at the inverter.
With the DC cables removed from the inverter and the isolator on, test the insulation resistance
for the DC wiring. This is a test between earth and the array positive lead. It is repeated
between earth and the array negative lead as well. The results expected will depend
on the system voltage.
[♪ Music ♪]
We suggest you test on the 1000v DC range with a result not less than 1 meg ohm.
If you have multiple strings you can check the DC short circuit current for the whole
system. It is as simple as turning off the array DC isolator, shorting out the DC leads,
turning on the DC isolator and using the clamp tester on DC amps. Measure and record the
results. Now just before you plug the DC leads into the inverter, check the polarity and
voltage. Make sure the polarity is correct otherwise you may damage the inverter and
void the warranty.
Ok, good job, now you've tested all the DC side of the installation, now you've got a
few tests of the AC side of the system before you can turn it on. This shouldn't be hard
as it is the same process that you use for any AC wiring testing.
First off, let's check the earth continuity.
Next, check the insulation resistance of the AC wiring. With the IR tester set to 500vDC,
the result should not be less than 1 meg ohm. On short distances, the result should be more
like 100 meg ohm.
The last test before powering up the system, is to check the AC voltage and the polarity
at the inverter. As part of your commissioning documentation, record these results on your
commissioning sheet.
So you have tested and checked the PV array on the roof and the DC and AC wiring at the
inverter and everything has checked OK.
Now you can power up the inverter, following the start-up instructions provided by the
inverter manufacturer.
Remember that the inverter cannot start feeding power until it has been connected to the grid
for one minute.
Now, the final check before handing over the system to the customer and putting out your
hand to get paid, is to check anti-islanding and ensure the system shuts down in less than
2 seconds if the grid is interrupted. The correct way to test this is to turn the grid-supply
main switch off (not the inverter main switch). This way there is still some load on the switchboard
and the anti-islanding must kick in and stop the inverter from generating power.
By testing your installation, you have not only complied with the requirements of the
Standards, but you have made sure that the installation is safe for your customer and
protected yourself against possible faulty workmanship.
[♪ Music ♪]
Just as testing is important, so is completing the documentation. It is proof that you tested
it and when a copy is left with the customer, it becomes a handy tool for system checking
later on. So, to re-cap, remember:
You must test an electrical installation - it is law.
Testing only takes a few minutes.
It safeguards you against potential faulty workmanship.
And if you are the electrician signing off on the paperwork, you are responsible for
the correct operation of the system.