Reliability Issues in Pv Systems – Experience and Improvements

A survey was conducted to collect information on faults, failures and poor performance from large PV plants a well as residential system like the ones of the »1000-Roofs-Programme«. The reason for a low energy yield in some systems was analysed. Modern modules built for a high voltage show very few failures. In one plant electrical faults affected 0.1 % of the total number of modules after two years of operation. Of these failures 90 % took place in junction boxes. Main reasons for low yield of the »1000-Roofs-Programme« systems were over-rated power of modules, partial shading of the array, soiling, faulty connections on the dc side and inverter failures. Failure analysis leads to recommendations for improved junction boxes. Modern Class II components offer the system designers more liberties. It may be appropriate to dismiss string diodes and string fuses, which results in simpler and more reliable systems.