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I-V400w - I-V500w - SOLAR I-Vw - SOLAR I-Ve
EN - 73
11.3.1. Typical errors on I-V curves and troubleshooting
Measurement
Event Troubleshooting
Good measurement
The measured curve extrapolated
to STC (blue) and the curve as
declared by the manufacturer
(black) of the modules match.
No error, save data and
move to next string to test
Low short circuit current
Irradiance sensor oriented
differently than the string under test
Reflections on the irradiance
sensor
Wrong module selection at
configuration of PV system
Environmental contaminants on
modules (soiling, dirt, snow, debris)
Far distance obstruction (shading)
Aging
Orient the irradiance sensor
properly
Set the instrument properly
Clean the modules
Remove obstruction
Check the modules for
blindness, humidity, etc.
Replace affected modules
High short circuit current
Irradiance sensor oriented
differently than the string under test
Shades on the irradiance sensor
Dirt on the irradiance sensor
Wrong module selection at
configuration of PV system
Irradiance sensor defect
Orient the irradiance sensor
properly
Clean the irradiance sensor
Remove obstruction
Check the irradiance sensor
for blindness, humidity, etc.
Set the instrument properly
Replace affected sensor
Low open circuit voltage
Low temperature measurement
Wrong numbers of module
selection at configuration of PV
system
Shorted bypass diodes
Attach the thermocouple
properly to a typical
temperature location
Select the AUTO mode
Set the instrument properly
Replace affected modules
Low current ratio Impp/Isc
Soiling across modules
Tapered shades
Small current mismatch
Degradation of cell shunt resistance
Clean the modules
Un-shade the modules
Check the current match
Replace affected modules
Low voltage ratio Vmpp/Voc
Voltage drop on cables to PV
module string
Check cables, connectors,
contacts, and string wirings
Check cable length and
cross section
Check modules for bad
connections or oxidation
Replace affected modules