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WET LEAKAGE TEST
Insufficient insulation allows moisture from rain, fog, dew or snow to reach a module’s voltage-carrying components. This can cause corrosion and short-circuits, and harbors considerable safety risks. As part of the wet leakage insulation-resistance test, a solar module’s insulation is measured under damp operating conditions.
The measurement process
The solar module is submerged horizontally in a container filled with a water-surfactant solution. The test ensures that all module surfaces (with the exception of the junction box), as well as the connectors (if present), are submerged. The cable entries are also wetted with the solution.
The short-circuited solar module outputs are connected to the positive pole, and a metal conductor connects the solution to the negative pole of a DC insulation tester with current limitations.
In the next step, the module is exposed to a voltage of 500 V, or, if higher, the maximum system voltage. The rate at which the voltage rises is limited to 500 V per second. Once the target value is reached, voltage is maintained for 2 minutes, and the connection’s insulation resistance is measured. After the measurement process is completed, voltage drops to zero, and the module is discharged by short-circuiting the dielectricmeter’s clamps.
Rating
- Modules with a surface area of less than 0.1 m2 should not have an insulation resistance lower than 400 Megaohms.
- In the case of modules with a surface area of more than 0.1 m2, the insulation resistance multiplied by the module surface area should not be lower than 40 Megaohms.
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