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Measuring 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).
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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).
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Inverter Mega
-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 insulation 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 photovoltaic 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
