Making Measurements
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Alerts.
The Array Tree closes and the I-V curve expands to its full width.
Inspect the curve for abnormal shapes. Also notice the values of the Fill Factor and the Performance
Factor below the I-V curve graph. Fill Factor gets smaller if the I-V curve is badly shaped. Expect
Performance Factors to be mostly in the 90-100% range for a new, clean array; if the values are way
higher or lower than that, check that the irradiance sensor is mounted in the plane of the array, that the
computer’s date, time, and time zone are correct, and that the 17 PV module parameters are correct, and
that your array azimuth and array type are correctly set.
Inspect the sensor values that were saved with the measurement. They appear directly below the I-V
curve graph.
Select the next PV circuit and take another measurement
Lift the previous fuse and insert the next one.
Repeat the above steps to make and save your measurement.
Be aware that when your measurements are all finished and the data is exported from the PVA
software, the software exports only the last measurement saved to each branch of the Array Tree. If you
take some extra measurements while troubleshooting a string that’s underperforming, be sure to take
one final measurement of the repaired string, for export.
View the consistency of your data before moving on
Before moving to the next combiner box or inverter, click on the History tab and scroll left-to right to
see the numerical results of the measurements at this combiner box. Your most recent measurement
appears in the left column.
For example, the Voc values should be closely grouped, indicating that the strings all have the right
number of modules.
The Isc values should be closely grouped as well, if it is a clear day and the irradiance is nearly
constant.
A low Fill Factor means that the shape of the I-V curve is degraded. This can be caused by shading,
soiling, or debris or equipment on the modules under test.
It is often helpful to clear the History table before moving on to the next combiner box.
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