EN
133
This means that if the system is made up of 10 modules in series and each one supplies 50V, the leakage can be located between the
4th and 5th PV module.
(+)
(-)
50 V
50 V
50 V
50 V
Va
50 V
50 V
1
2
3
4
7
8
5
6
9
10
Vb
50 V
50 V
50 V
50 V
Va = voltage measured b pole and = 200V
Vb = voltage measured between - pole and = 300V
In all measurements with , the ground of the inverter is indicated.
8.13 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.
