Low Insulation Resistance

What does Low Insulation Resistance mean?

This alarm indicates that the insulation resistance of a PV string is low, suggesting a potential short-circuit. The inverter provides a percentage for the possible short-circuit position, with 0% representing the PV- terminal and 100% representing the PV+ terminal. Other percentages indicate a fault on a PV module or cable within the PV string, with a detection precision of ±1 PV module.

• Damaged connector or DC cable between PV modules and optimizers.
• Damaged connector or DC cable between adjacent PV modules and optimizers.
• Faulty PV module in the string.
• Faulty optimizer connected to the PV string.

Click steps to track your progress.

1. 1

   Refer to the 'Alarm details' page to check the percentage for possible short-circuit positions and calculate the likely fault location (Total number of PV modules in a PV string x Percentage of possible short-circuit positions).

2. 2

   Set the DC switch to OFF. Inspect the connector or DC cable between the possible faulty PV modules and corresponding optimizers, or those between the adjacent PV modules and optimizers for damage. Replace any damaged connector or DC cable.

3. 3

   Set the DC switch to OFF. Disconnect the possible faulty PV modules and corresponding optimizers from the PV string. Connect a DC extension cable with an MC4 connector to the adjacent PV modules or optimizers. Set the DC switch to ON and observe if the alarm clears.

4. 4

   If the alarm clears after disconnecting a PV module and optimizer, determine which component is faulty: Disconnect the PV module from its optimizer, then connect the optimizer to the PV string. Set the DC switch to ON. If the alarm is not reported, the PV module is faulty. If the alarm is still reported, the optimizer is faulty.

5. 5

   Set the DC switch to OFF and replace the identified faulty component (connector, DC cable, PV module, or optimizer).