Open string circuit

An open circuit is a break in the current path of a module substring, a whole module or a full string, so that part stops producing. Common causes are connector defects, damaged DC cables and junction box failures, including cold solder joints and loose or corroded contacts. In IR thermography under load, an open substring or module string looks warmer than the active strings. A full string loss can be seen this way too, but the faulty module can stay hard to locate. Electrically, an open substring loses its power and lowers module Voc. A string Voc check against identical strings or the expected value also catches missing interconnections. In monitoring data, look for a loss in performance and compare string currents to find the string that is underperforming. To tell the causes apart, first inspect connectors and cables visually and by touch under safe isolation. Then check junction boxes for burn marks, open lids or detachment, and use IR to find hot connections. If an open circuit traces back to the junction box, replacing the module is advised because repairs may start new fires.

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• sentence 1: support check: partial - Passages describe open-circuited module/cell strings and substring power loss, but do not define an open circuit as a break in the current path; it is mostly implied.
• sentence 4: support check: partial - Substring power loss and Voc reduction are stated, and string Voc comparison catches missing interconnections, though the latter is about missing module interconnections in strings rather than open substrings specifically.
• sentence 6: support check: partial - Visual/tactile inspection under isolation and IR are supported, and junction box visual/thermal inspection is stated, but the sequencing and specific checks for burn marks, open lids or detachment are only partly in the passages, though lid defects and burnt boxes are mentioned. -->