Event 3501
Qualified person
Event message:
Insulation failure
Check generator
Explanation:
The insulation resistance of the DC installation is or was too low. The inverter disconnects from the utility grid for safety reasons and/or fails to connect during self-test mode. The cause is often defective insulation or a faulty plug connection on the PV modules or within the DC wiring. The event message can occur temporarily as it is influenced by ambient conditions such as rain or dew. In addition, mechanical influences (e.g. strong wind) can cause live DC cables to come into contact with grounded system parts if the cable insulation is defective. Inverters without a transformer can be destroyed by an ground fault during operation.
Corrective measures:
Check the frequency and duration of the event message in the inverter's user interface or in the Sunny Portal. The measurements listed below should be performed under the same ambient conditions and at the same time of day as when the error occurred—ideally while an event message is active.
If module electronic components, such as SunSpec-compatible module disconnectors, are present, an additional device is required to maintain the SunSpec PLC signal.
Verify through measurement of the open-circuit voltage of the PV strings that the measured values correspond to the system design and prevailing irradiation conditions.
Measure the voltage of each PV string between DC+ and PE, and between DC− and PE, using a suitable measuring device. If a stable voltage is measured that approximately equals the string voltage, this indicates a ground fault. Correct the ground fault on the relevant PV string and only then reconnect.
Measure the insulation resistance of each PV string using an insulation resistance meter. Ensure that the PV string is short-circuited during these measurements and that the maximum permissible system voltage of the PV modules is not exceeded. If the insulation resistance is too low, it indicates a ground fault. Correct the ground fault on the relevant PV string and only then reconnect.
Visually inspect the entire DC installation (PV modules, cables, plug connections, and any existing components such as module optimizers or disconnectors) to ensure there are no signs of damage, such as porosity, cracks, crushing, deformation, or discoloration. Replace or repair any defective components.
Tip: Use an IR camera for support.