SMA SUNNY TRIPOWER X 20-US - Calculating the Insulation Resistance

11 Troubleshooting
SMA Solar Technology AG
Operating manual STPxx-US-50-BE-en-11 87
Corrective measures:
• Check the configuration of the Rapid Shutdown function and ensure that the operating mode
selected is selected according to the DC disconnection unit used.
• Check the functionality of the PV array disconnect switches.
• Check the standby voltage of the PV array disconnect switches used and ensure that the
standby voltage of all PV array disconnect switches of a string < 30V.
11.1.44 Event 9035
Event message:
• Rapid Shutdown successfully performed.
Explanation:
The voltage at the DC inputs and at the AC output of the inverter was successfully discharged.
11.1.45 Event 9038
Event message:
• Redundant Rapid Shutdown discharge function not ensured.
Explanation:
The cause must be determined by the Service.
Corrective measures:
• Contact the Service.
11.2 Calculating the insulation resistance
The expected total resistance of the PV system or of an individual string can be calculated using the
following formula:
The exact insulation resistance of a PV module can be
obtained from the module manufacturer or the datasheet.
total
The exact insulation resistance of a PV module can be obtained from the module manufacturer or
the datasheet.
For the resistance of a PV module an average value can be assumed: for thin-film PV modules
approximately 40MOhm and for polycrystalline and monocrystalline PV modules
approximately50MOhm per PV module.
Also see:
• Checking the PV System for Ground Faults⇒page88