169Maintenance
EN
8.14 Measuring the isolation resistance of the PV
generator
WARNING – B The operator must always use the personal protective equipment (PPE) required
by the laws of the country of destination and whatever is provided by their employer.
To measure the isolation resistance of the PV generator compared to ground , the two poles of the PV
generator must be short-circuited (using a suitable sized switch).
WARNING – B Use of unappropriate sized switch could cause risk of fire or electric arc! Use only
1500V rated switch!
+
_
IG
Once the short-circuit has been made, measure the isolation resistance (Riso) using a megohmmeter
positioned between the two shorted poles and ground (of the inverter).
Mega
Inverter
IG
+
_
If the measured isolation resistance (Riso) is less than 75 kOhm, the inverter may not connect to the grid
because of low isolation of the PV generator to ground.
ATTENTION – A The isolation resistance can be affected by the environmental conditions the PV
generator is in (E.g.: PV modules wet from damp or rain), and therefore the measurement must
be made immediately after the anomaly is detected.
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