10 Troubleshooting
SMA Solar Technology AG
Operating manualSTP15-25TL-30-BE-en-1772
Required devices:
☐ Suitable device for safe disconnection and short-circuiting
☐ Measuring device for insulation resistance
Device required for safe disconnection and short-circuiting of the PV array
The insulation resistance can only be measured with a suitable device for safe disconnection
and short-circuiting of the PV array. If no suitable device is available, the insulation
measurement must not be carried out.
Procedure:
1. Calculate the expected insulation resistance per string.
2.
DANGER
Danger to life due to high voltages
• Disconnect the inverter from all voltage sources (see Section11, page76).
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. Reconnect to the inverter only those strings from which the ground fault has been eliminated.
11. Reconnect all other strings to the inverter.
12. Recommission the inverter.
13. If the inverter still displays an insulation error, contact the Service (see Section16, page91).
The PV modules might not be suitable for the inverter in the present quantity.
10.5 Checking the Function of the Surge Arresters
Surge arresters are wearing parts. Their functionality diminishes with age or following repeated
exposure to overvoltage. It is therefore possible for the surge arresters to lose their protective
function over time.
Check the function of the surge arresters as described in the following.
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