Study of Partial Discharge effects of PV backsheet component films. Structure property relationships, and measurement consistency

Partial Discharge is one of a number of tests defined in IEC61730–2, which specifies properties of photovoltaic modules and components for safe electrical and mechanical operation during their expected lifetime. The test is of practical importance in the development and manufacturing of backsheet barrier films because of the limitations it places on film thickness. The objective of this study was to understand the relationship of this test to film properties. Although simple to describe, in practice, the test is difficult to perform with consistency. We have found that this test performed in air usually provides consistent relative behavior, but that absolute values can vary on different days, or in different laboratories. We have tested several materials with varied thickness, and found a linear relationship between Ve and square root of film thickness when measured in air, in line with a surface discharge phenomenon. This paper will describe efforts to define and understand sources of variability in both inter and intra laboratory measurements, and on the measurements of some typical component materials of PV backsheets.