Electrical and thermal finite element modeling of arc faults in photovoltaic bypass diodes.

Abstract

Arc faults in photovoltaic (PV) modules have caused multiple rooftop fires. The arc generates a high-temperature plasma that ignites surrounding materials and subsequently spreads the fire to the building structure. While there are many possible locations in PV systems and PV modules where arcs could initiate, bypass diodes have been suspected of triggering arc faults in some modules. In order to understand the electrical and thermal phenomena associated with these events, a finite element model of a busbar and diode was created. Thermoelectrical simulations found Joule and internal diode heating from normal operation would not normally cause bypass diode or solder failures. However, if corrosion increased the contact resistance in the solder connection between the busbar and the diode leads, enough voltage potential would be established to arc across micron-scale electrode gaps. Lastly, an analytical arc radiation model based on observed data was employed to predicted polymer ignition times. The model predicted polymer materials in the adjacent area of the diode and junction box ignite in less than 0.1 seconds. 4 ACKNOWLEDGMENTSThis work was funded by the US Department of Energy Solar Energy Technologies Program.5

Fire safety of building integrated photovoltaic systems—State of the art

“…It takes less than 0.1 s to ignite the polymer back layer and the polymer materials in the region adjacent to the diode and junction box (Bower et al, 2012). In addition, the accumulation of impurities (e.g., oxide) on electrical contacts can cause resistive heating, resulting in breakdown of materials and subsequent arcing (Gholami et al, 2015).…”