A method for detecting a contact fault in a photovoltaic system is disclosed. The photovoltaic system includes an inverter and a photovoltaic generator connected to the inverter via DC current lines. The inverter includes a transmitter for coupling a first AC voltage signal having communication frequencies in a first frequency range between 125 kHz and 150 kHz into the DC current lines. A receiver is configured to couple out the first AC voltage signal and is arranged at the photovoltaic generator. A decoupling circuit is configured to decouple the impedance of the photovoltaic generator is arranged between the inverter and the photovoltaic generator, such that the photovoltaic generator is AC decoupled from a transmission path between the inverter and the decoupling circuit. The inverter communicates with the receiver via the first AC voltage signal, and wherein AC currents are measured in the DC current lines and AC voltages are measured between the DC current lines to aid in detection of a contact fault condition.