PV System Commissioning: Page 2 of 2

Tests and Tools
Intermediate

Inside this Article

Fluke Meter
A Fluke Meter
Measuring PV output
Measuring the array’s output during operation (DC voltage and current, and calculating power). Low irradiance (at top of screen) causes the very low kW measurement.
A ground continuity test
A ground continuity test—One clamp is attached at the main ground wire (EGC) going to the ground rod at the pole-mounted array. The other clamp (not pictured) is attached to the module frame. Voltage-rated insulated gloves should always be worn when making electrical connections for specific commissioning procedures.
The Seaward PV150 Solar Installation Test Kit
The Seaward PV150 Solar Installation Test Kit (with 200R irradiance meter).
A performance validation test
A performance validation test measures irradiance, cell and ambient temperatures (not shown), DC input voltage and current, and AC output voltage and current. The Hukseflux Solar I-V automatically calculates DC and AC efficiencies based on these measurements.
Hukseflux Solar I-V and components.
The Hukseflux Solar I-V and its components.
A temperature sensor
A sensor placed on the module backing measures cell temperature.
Irradiance measurement
The Seaward Solar 200R measures the irradiance (w/m2) on the array. This measurement, along with the cell temperature, is used in performance verification calculations.
Average IV curve for a module
This shows a typical, average IV curve for a module. Here, the string measurements were averaged to calculate the average module IV curve for comparison to manufacturer’s data.
Typical power curve for an entire string
A typical power curve for an entire string—in this case, ten 240 WDC modules in series.
Performance analysis test results
The performance analysis test results showing DC performance measurements for a 2,400-watt array.
The Hukseflux irradiance meter
The Hukseflux irradiance meter includes calibrated multi- and monocrystalline PV cells for accurate irradiance measurements.
The Solar02 transmitter
The Solar02 transmitter combines the temperature and irradiance readings into one unit that can transmit data back to the meter through radio frequency (RF) or record data that is synchronized with the main Solar IV meter when that unit is out of RF range.
Infrared camera (detail)
Infrared camera
Infrared camera (In Use)
Infrared cameras give installers a quick way to identify the source of array performance problems. Additionally, the images can be helpful in supporting a warranty claim.
Fluke Meter
Measuring PV output
A ground continuity test
The Seaward PV150 Solar Installation Test Kit
A performance validation test
Hukseflux Solar I-V and components.
A temperature sensor
Irradiance measurement
Average IV curve for a module
Typical power curve for an entire string
Performance analysis test results
The Hukseflux irradiance meter
The Solar02 transmitter
Infrared camera (detail)
Infrared camera (In Use)

Commissioning Tools

Several manufacturers offer testing equipment for PV system commissioning, including the following products:

Seaward PV150 Solar Installation Test Kit, which includes the meter, leads, and AC/DC current clamp ($1,495). This device can perform all the minimum IEC 62446 commissioning tests (except performance verification) with the push of a button. It is designed to connect directly to MC4 output and can safely perform the short-circuit current measurement using an internal switch. The PV150 performs the insulation resistance testing of a module or string by safely shorting the array output (+ and -) and applying the appropriate test voltage between the shorted outputs and ground. (Note: Some methods of testing that involve measuring megohms of insulation resistance between a positive and ground or the negative and ground may damage the module or diodes and/or void module warranties.)

The PV150 can also measure irradiance, and ambient and cell temperatures simultaneously during all the test measurements used in performance verification calculations with its optional 200R irradiance meter ($475). (Note: The 200R has radio frequency communications with PV150 and the ability to download the data to a computer.) By using the separate clamp-on meter, you can verify the inverter efficiency.

There are other advanced tools that provide additional analyses and troubleshooting ability. If the system you’re testing does not pass the IEC 61446 commissioning tests, these tools can help find the problem quickly. They are not required for standard IEC 62446- or NABCEP-recommended commissioning, but are briefly mentioned in both of those documents.

Hukseflux Solar I-V($5,625) combines the I-V400 curve tracer ($4,165) and parts of the Solar300 ($7,595). The Solar I-V can test each module or string’s IV curve, and the output performance of a single-phase AC circuit from the inverter with one DC input into the inverter during operation, up to a maximum of 1,000 VDC and 10 A. Voltage-current curve tracing of installed modules and strings is useful to ensure they are matched and offers a good baseline for future performance validation and troubleshooting. This level of testing is not really necessary for most residential systems, but is becoming necessary for bank-financed utility-scale projects that are expected to give a minimum return on the investment. These tests were done on the Cloudview installation (see the “Commissioning Cloudview” sidebar).

Flir E40 infrared thermal imaging camera ($3,995) is helpful for detecting module defects, since it can show “hot spots” on modules, revealing problems like  internal module wiring issues or failed diodes, which can be responsible for reducing the module’s output. Thermal cameras are also useful for checking system connections, since loose or improperly torqued connections are hotter than other connections because of increased resistance. Like the IV curve tracer, these are not generally used in a typical residential installation except to troubleshoot problems that have been indicated by the other measurements.

Access

Bill Hoffer has worked in the solar industry for more than 20 years. He is an alumnus of Solar Energy International, where he now teaches. Bill also consults with manufacturers in product development and testing, and specializes in the third-party commissioning, performance validation, and troubleshooting for commercial- and utility-scale systems.

Testing Equipment:

Flir E-40 infrared thermal camera • Flir • flir.com

Hukseflux Solar IV curve tracer • Hukseflux USA • huksefluxusa.com 

Seaward PV150 • Seaward Solar USA • seawardsolar.com

Comments (3)

Marc Fontana's picture

Great Article ! One question - the caption below the center photo of the Array Power Curve on page 63 reads "...240 VDC modules in Series" Is this a typographical mistake or is the voltage of the whole string? The screenshot shows a Voc of 342 volts (34.2 volts per module). Shouldn't this caption be 240W DC?

Scott Russell's picture

The online version of the article has been corrected. Thanks for keeping us on our toes, Marc. -Scott, HP

Joe Schwartz's picture

Great catch, Marc! That was a typo on our part and you are correct that the caption should have stated "240 W DC". Thanks again for your sharp eye. -Joe, editor

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