HT SOLAR I-Ww User Manual page 76

Steps in the I-V curve
Characteristic curve not linear
I-V400w - I-V500w - SOLAR I-Vw - SOLAR I-Ve
 Small or partial shading of one
module of the string under test
 Reflections
 Random
contaminants on modules (soiling,
dirt, snow, debris, etc.)
 Strong current mismatch
 Cracks of cells or glass
 Burn marks
 Unsteady
irradiation
measurement
 Leopard spot clouds shading the
modules
 Low
irradiation
measurement
EN - 74
 Remove obstructions
 Re-test when un-shaded
 Remove reflections
environmental  Clean the modules
 Check the current match
 Replace affected modules
 Re-test when clouds are
during
gone
 Repeat measurement at an
irradiation of minimum
700W/m
during
2
(IEC/EN61829)