PV MODULE PRE-SHIPMENT INSPECTION
KNOW CAUSES OF FAILURES AND CONSEQUENCES FOR
– PV CELL STRING SHORT CIRCUIT
– SAFETY DISTANCE NOT MET BETWEEN THE CELL AND THE GLASS EDGE
– BROKEN CABLE
There are several important items to check before the PV module shipment. Typically pre-shipment inspection consists of visual inspection, dimensions measurement, EL inspection, insulation test witness, and maximum power determination. The intent is to ensure that the shipments meet all the buyer’s requirement. We regularly capture non-conformities to the requirements during this step, and very often, these are caused by improper operation. Here are a few recent examples:
– PV Cell String Short Circuit
Cause of Failure: There is excess soldering tin in the welding process of the junction box, which makes the two terminals overlap, resulting in a short circuit of one of the cell strings inside the module.
Consequences: 1) The module power is reduced by about 35%; 2) All the current will flow through the soldering overlap, which may create a local hot spots.
– Safety distance not met between the cell and the glass edge
Cause of Failure: An offset in the cell lay-up process resulted in misplacement of the cells with respect to the edge of the glass after lamination. The resulting distance does not meet the IEC/UL requirements for safety distance between the cell and the glass edge.
Consequences: If deployed, these modules will likely not meet the local safety requirements and may therefore need to be removed from the plant. Electrical safety risks may also exist.
– Broken Cable
Cause of failure: If the assembly line is not well adjusted, there may be some friction between the cable and the assembly line surface.
Consequences: There will likely be electricity leakage on the damaged position of the cable, leading to safety risks and tripping of the fuse during operations.