SMA STP 50-40 Operating Manual page 113

SMA Solar Technology AG
3. Measure the voltage between the negative terminal and the ground potential (PE).
4. Measure the voltage between the positive and negative terminals.
5. If the following results are present at the same time, there is a ground fault in the PV system:
☑ All measured voltages are stable.
☑ The sum of the two voltages to ground potential is approximately equal to the voltage
between the positive and negative terminals.
6. If a ground fault is present, determine the location of the ground fault via the ratio of the two
measured voltages and eliminate the ground fault.
7. If a definite ground fault cannot be measured and the message is still displayed, measure the
insulation resistance.
8. Reconnect the strings without ground faults to the inverter and recommission the inverter (see
inverter installation inverter).
Location of the ground fault
The example shows a ground fault between the second and third PV module.
100 V
Test by Measuring the Insulation Resistance
If the voltage measurement does not provide sufficient evidence of a ground fault, the insulation
resistance measurement can provide more exact results.
Operating manual
V = 200 V
1
100 V
+
V = 300 V
2
100 V 100 V
STP50-4x-BE-en-23
11 Troubleshooting
100 V
113