Overvoltages in photovoltaic systems induced by lightning strikes

The high number of photovoltaic systems raises questions regarding their operational security even under extremely weather conditions like thunderstorms. Therefore a simplified model of a photovoltaic system, consisting of typical arrangement of solar-panels, was investigated. The influence of lightning strike was simulated by different lightning current shapes and striking points into the solar-panels. It was found, that besides the construction size and shape of the lightning current the striking point has a main influence on the value of induced overvoltages, occurring on the connection point of the solar-panels. The simulation results were confirmed by measurement with an impulse current. The results demonstrate the dangerousness of lightning currents with very fast rise time e.g. subsequent impulse as well as the reducing of induced overvoltages by an appropriate earthing connection. This has to be considered at the design of the lightning protection system.