An open failure of the bypass diode (BPD) of a photovoltaic module can damage the cell. With existing inspection methods, it is difficult to find an open failure of a BPD. A method for finding open failure of BPDs using thermal imaging was investigated. The following points were clarified in this study. In a partially shaded cell, the unshaded portion of the cell generates heat. There are two types of heating: surface heating and point heating. They occur simultaneously. Point heating causes the back sheet to burn. However, if the shaded area is 10%, the cell does not burn as a result of point heating for a long time. Surface heating can cause the heat generation temperature of the cell surface to become high. The heat generation temperature can be adjusted by setting the number of shaded cells so that multiple cells are shaded. The heat generation temperature of a partially shaded cell differs depending on whether the BPD is open.
