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
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. .