A photovoltaic system having a photovoltaic generator, whose strings with series-connected photovoltaic modules have a positive pole and a negative pole, and with an inverter whose DC input is connected to the two poles. The voltage of the positive pole and/or of the negative pole is measured with respect to ground, and a first switching element located between the positive pole and the DC input of the inverter and/or a second switching element located between the negative pole and the DC input of the inverter is opened, while a third switching element located between the positive pole and the negative pole is closed, when the voltage of the positive pole or of the negative pole exceeds a predefined first or second limit value.