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000043DG
8 - Maintenance
M
easuring the insulation resistance of photovoltaic generator
To measure the insulation resistance of the PV generator compared to
ground , the two poles of the PV generator must be short-circuited
(using a suitably sized switch).
+
_
IG
Once the short-circuit has been made, measure the insulation resistance
(Riso) using a megohmmeter positioned between the two shorted poles
and ground (of the inverter).
Mega
Inverter
IG
+
_
-TL MODELS (transformerless).
If the measured insulation resistance
(Riso) is less than 1Mohm the inverter does not connect to the grid due
to a low insulation of photovoltaic generator respect to ground.
-I MODELS (with high frequency transformer).
If the measured insu-
lation resistance ( Riso in case of input poles floating respect to ground
or QF=1 if the one of input poles is grounded) is less than 0.2Mohm the
inverter does not connect to the grid due to a low insulation of photovol-
taic generator respect to ground.
The insulation resistance is affected by the
environmental conditions the PV generator is in
(E.g.: photovoltaic module wet from dump or rain), and therefore the measurement must be
made immediately after the anomaly
