Sandia National Labs researchers have made a new dataset about the rates and types of PV connector errors on the roof. Their analysis has shown that tight bending radius, extra dirty connectors and loose nuts are the most common failure causes in 6,276 connectors that were used in seven American regions between 2014 and 2017.
A group of scientists from the Sandia National Laboratories of the US Department of Energy has performed a failure analysis of 6,276 Fotovoltaic connectors used in PV systems on the roof, in an attempt to increase publicly available data on the rates and types of connector errors.
“The primary goal is to set up a field connector database that includes the installations that are representative of the entire PV industry and provides insights into installation practices, connector models, climates and other system variables associated with the highest error rates,” the academics explained. “The research will also include forensic analysis to identify the root causes of failures.”
The group has all connectors for the analysis from a non -known PV system system that is active on the American market. The devices were installed between 2014 and 2017 and were from 265 individual roof systems spread over seven American regions, with California resulting in the highest number.
For their failure analysis, the researchers implemented a framework, including barcoding, wire strips, visual inspection, 4-thread resistance measurements and X-ray image formation.
“This characterization procedure priority gave high efficiency and fast connector processing over measurements with high accuracy,” they specified. “The full data set of this work is hosted on the Duramat Data Hub. All data analysis was performed using Python scripts and from bijters were identified using the Interquartile Range (IQR) method.”
The analysis showed that tight bending radius, extra dirty connectors and loose nuts are the most common failures in PV systems on the roof, with percentages of 2.2%, 1.3%and 1.1%respectively. Moreover, the scientists found that loose nuts had a critical percentage of 41 % for fiber optic connectors.
They also found that high power levels are often associated with the higher resistance ranges of connectors and critical failure percentages, which were attributed to resistive heating.
In addition, the research team has carried out a performance assessment of cross-mated connector models. “The analysis did not reveal a definitive performance trend between cross-mated and non-cross-mated connectors; some long-term connectors performed adequately, while others did not do that,” they noticed.
The analysis also showed that connector types that are designed to limit heat disipation, from contact to the housing are often associated with higher failure percentages, and that completed contact bars used in some connectors can lead to errors of fixed posture.
The connector analysis was presented in the study “Fast characterization and failure analysis of 6276 on the roof harvested photovoltaic connectors“Published in Solar energy. “Future work will use the techniques developed in this article to characterize a more diverse range of PV installations,” the team concluded.
Other researchers from Sandia National Labs have recently created a standardized terminology for PV connectors in an attempt to reduce confusion and offer best practices for their implementation.
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