EN
75
8.5 Verification of ground leakage
In the presence of anomalies or report of ground fault (where
provided), there may be a ground leakage from the PV generator
(DC side).
To check this, measure the voltage between the positive pole and
ground and between the negative pole (of the PV generator) and
ground using a voltmeter whose input accepts a voltage sufficient
for the dimensions of the photovoltaic generator.
8.5.1 Behaviour of a system without leakage
Due to the capacitive effect of the PV generator, during the first
moments that the voltmeter is connected between one of the two
poles and ground, it will measure a voltage of about Voc/2, which
will tend to stabilize to around 0V if there is no ground leakage, as
shown in the graph below:
Voc
V
t
+Vs
-Vs
NOTE –
D
The internal resistance of the voltmeter tends
to zero the voltage present on the PV generator due to the
capacitive effect.
How to make the measurement:
Volt
(+)
(-)
8.5.2 Behaviour of a system with leakage
If the voltage measured between one of the two poles and ground
does not tend to 0V and stabilizes on a value, there is a ground
leakage from the PV generator.
Example: When the measurement is made between positive pole
and ground, a voltage of 200V is measured.
V
200 V
300 V
t
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.
