SMA STP 12000TL-US - Manual (Page 59)

Example: Location of the ground fault
The example shows a ground fault between the second and third PV module.
3. If a definite ground fault cannot be measured and the message is still displayed, measure the
insulation resistance.
4. Reconnect the strings without ground faults to the inverter and recommission the inverter (see
Section 11, page 61).
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.
Required devices:
☐ Suitable device for safe disconnection and short-circuiting
☐ Measuring device for insulation resistance
Procedure:
1. Calculate the expected insulation resistance per string.
2.
Danger to life due to high voltages
• Disconnect the inverter from all voltage sources (see Section 9, page 41).
3. Install the short circuit device.
4. Connect the measuring device for insulation resistance.
5. Short-circuit the first string.
6. Set the test voltage. The test voltage should be as close as possible to the maximum system
voltage of the PV modules but must not exceed it (see datasheet of the PV modules).
7. Measure the insulation resistance.
8. Eliminate the short circuit.
9. Measure the remaining strings in the same manner.
☑ If the insulation resistance of a string deviates considerably from the theoretically
calculated value, there is a ground fault present in that string.
10 Troubleshooting SMA Solar Technology AG
Installation Manual 59 STP12-24TL-US-IA-en-16