Sequential Application of Static and Dynamic Mechanical Loads for Electrical Isolation of Cell Cracks
Colin Sillerud, Kyumin Lee, Jim Crimmins
CFV Solar Test Laboratory, Albuquerque, NM, United States

The static mechanical load test (SMLT; IEC 61215 series) and the dynamic mechanical load test (IEC TS 62782:2016) are widely used in the industry to mimic the mechanical stresses in the installation and operation of PV modules. The DMLT is often followed by thermal cycling and humidity-freeze cycling; the DMLT-TC50-HF10 sequence appears in the new CSA/ANSI C450 standard published in 2018. The EL images of field-stressed modules, however, show higher degree of electrical isolation of cell cracks (“islanding”) than what is observed in modules stressed by SMLT or DMLT-TC50-HF10. Such qualitative difference raises questions on the validity of post-MLT power measurements. We investigated different MLT variations of the DMLT-TC50-HF10 sequence and found that a sequential execution of SMLT and DMLT is effective in creating and then electrically isolating the cell cracks.