SMA SB 1300TL Service Manual - Manual (Page 19)

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 2.2, page 7).
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 the that string.
10. Reconnect only those strings to the inverter from which the ground fault has been eliminated.
11. Reconnect all other strings to the inverter.
12. Recommission the inverter (see Section 5, page 22).
13. If the inverter still displays an insulation error, contact the SMA Service Line. The PV modules
might not be suitable for the inverter in the present quantity.
4.2.3 Checking the Function of the Varistors
Figure 2: Varistors inside the inverter
Position Designation
A Upper varistor lead
4 Troubleshooting SMA Solar Technology AG
Service Manual 19 SB13-21TL-SG-en-11