Three-circuit voltage spike protection for a photovoltaic system

The system (1) has first and second switching elements (17, 19) connecting positive and negatives poles (11, 13) to a direct-current (DC) input of an inverter (5). The switching elements are opened by a control device (23) when voltages of the poles exceed respective predetermined threshold values with respect to ground. The control device closes a third switching element (21) arranged between the poles when the first and second switching elements are opened, where the closed third switching element interconnects the poles. The switching elements are designed as switches. The threshold value is equal to or smaller than 3 percent of value of a lowest permissible voltage strength of all components such as clamp and cable of a photovoltaic module.