2 Error Messages Relating to the PV Array SMA Solar Technology AG
4 Fehleranalyse-SG-en-10 Service Manual
2 Error Messages Relating to the PV Array
Analysis/Test Data/Measured Values
• When does the error occur?
–regularly?
Matching the data sheet specifications with the
design or the measured values of the system.
– always at the same time of day? V
0C
(open-circuit
voltage):
– only when irradiation is good?
– only in humid/wet weather? I
SC
(short-circuit current):
– when it is snowing?
– at dawn/dusk? MPP-voltage:
– in other inverters in the system as well?
• Have strings been swapped? String currents:
• Does the error also occur in each separate string?
• Before connecting the strings to the inverter, the strings must be
checked for the correct polarity, insulation and compliance with
the voltage limits.
Insulation resistance
measurement (in ohm):
• With multistring inverters, make sure that the positive and
negative terminals of a DC string are connected to the same
MPP tracker.
DC+ to PE (V):
DC– to PE (V):
• The design must match the start voltage, the MPP voltage and
the maximum allowable DC voltage for the inverter.
• Shading, snow or pollution can affect the feeding behavior
considerably.
• Possible module defects can be identified via characteristic
curve measurements. Provided the appropriate equipment is
available, thermographic measurements of the modules or
electroluminescence procedures can be used.
• Insulation errors must be carefully monitored and rectified if
they occur. Visual inspections of the modules and the DC cable
position as well as insulation resistance measurements and
ground fault tests are part of it.
• The errors can also occur sporadically due to the weather
(moisture, movable cable position).
• The minimum permitted insulation resistance Riso depends on
the inverter type and firmware version.
• The capacitive leakage currents with transformerless inverters
must be considered. These are linked to the type, installation
and quantity/area of the PV modules used. Commissioning the
first string and then the remaining strings one after the other can
provide information. The grounding connection at the inverter
and in the subdistribution must also be tested in these cases.
Reverse polarity and "multiway switch" ruled out?
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