A photovoltaic system , comprising at least one string of series-connected solar modules and an inverter for converting the direct current generated by the string ; wherein in the normal state, the positive end of the string is connected, via a positive pole string line , to the positive pole DC input of the inverter , and the negative end of the string is connected, via a negative pole string line , to the negative pole DC input (91 b) of the inverter ; wherein a test circuit is comprised, which is connected in the positive pole string line between the positive end of the string and the positive pole DC input of the inverter , and/or in the negative pole string line between the negative end of the string and the negative pole DC input of the inverter ; wherein the test circuit includes at least a first switch for disconnecting the positive pole string line between the positive end of the string and the positive pole DC input of the inverter , or for disconnecting the negative pole string line between the negative end of the string and the negative pole DC input of the inverter ; characterised in that the inverter includes a DC-side capacitor ; wherein, in an inverter-side testing process , the test circuit opens the first switch so as to disconnect the DC-side capacitor of the inverter from the string and/or from a voltage supply of the test circuit , at least at one side; and wherein the test circuit is responsive to a voltage drop caused by the disconnection of the DC-side capacitor of the inverter to determine whether the inverter is actually connected to the string lines at that moment and/or whether the inverter-side section of the string lines is closed or not. wherein in the normal state, the positive end of the string is connected, via a positive pole string line , to the positive pole DC input of the inverter , and the negative end of the string is connected, via a negative pole string line , to the negative pole DC input (91 b) of the inverter ; wherein a test circuit is comprised, which is connected in the positive pole string line between the positive end of the string and the positive pole DC input of the inverter , and/or in the negative pole string line between the negative end of the string and the negative pole DC input of the inverter ; wherein the test circuit includes at least a first switch for disconnecting the positive pole string line between the positive end of the string and the positive pole DC input of the inverter , or for disconnecting the negative pole string line between the negative end of the string and the negative pole DC input of the inverter ; the inverter includes a DC-side capacitor ; wherein, in an inverter-side testing process , the test circuit opens the first switch so as to disconnect the DC-side capacitor of the inverter from the string and/or from a voltage supply of the test circuit , at least at one side; and wherein the test circuit is responsive to a voltage drop caused by the disconnection of the DC-side capacitor of the inverter to determine whether the inverter is actually connected to the string lines at that moment and/or whether the inverter-side section of the string lines is closed or not. <EOS>