News & Events
September 14-17, 2015
Anaheim Convention Center
Visit 3M at Booth #4546
Study of Partial discharge effects of PV Backsheet Component Films. Structure-property relationships and measurement consistency.
This paper describes the physical properties which give rise to a partial discharge signal when measured on polymeric PV backsheets. When performed in air, measured extinction values are related to the dielectric constant and thickness of the material, and is not related to a “partial discharge” across a void in the material. When the test is performed in oil, a partial discharge across an embedded air void can be observed.
Study of partial Discharge Effects of PV Backsheet (PDF 199KB)
Analytical Techniques Used to Determine Chemical Degradation of Polymeric Materials Used in PV Modules after Sustained Exposure to Partial Discharge Voltages
It has been suggested that the “partial discharge test” performed in air is a useful method to measure surface discharges which could be damaging to polymeric backsheet. The test performed in air does measure surface discharge, but does not measure a material’s resistance to electrical degradation. This was demonstrated using x-ray photoelectron spectroscopy (XPS or ESCA) to characterize the surfaces after prolonged exposure at voltages where surface discharge occurs. Based on the materials model, the utility of the partial discharge test for PV polymeric materials is suggested as in the table.
Table 2. Partial Discharge Testing and Materials Properties
Analytical Techniques PV Modules Partial Discharge Voltages (PDF 1.17MB)
Understanding Polymer Degradation under Voltage Stress in PV Applications
The very significant differences in the applicability of the PD test performed in air and oil for PV backsheets are demonstrated by taking measurements of laminated materials with large, visible air bubbles, in comparison with materials with none. Using the PD (air) test, materials with large air bubbles were indistinguishable from the material with no bubbles, while with the PD (oil) test, significant differences were observed. A second concern is the use of an AC test for a DC system. DC breakdown occurs by different mechanisms than for AC, and does not have a consistent ratio to AC measurements, and does not have the same voltage endurance profile.
Figure 4. AC and DC Voltage endurance plots for 125 µm PET.
Polymer Degradation Under Voltage Stress in PV Applications (PDF 545KB
Quantifying PV module microclimates, and translation into accelerated weathering protocols
A simple model for characterizing in-service environments using real-world data and established PV module temperature models.
Quantifying PV Module Microclimates (PDF 619KB)