System for diagnosing the condition of at least two sections of two direct current, DC, lines (20, 21), the system comprising a device for diagnosing the presence of an electric current flowing through a section of a direct current, DC, line, the device comprising: - a current generator adapted to deliver an alternating current, AC, to said section to be diagnosed, - a first and a second electrical terminals (A, B), and - a computing or electronic module for verifying if the delivered current flows through said section, characterized in that the system further comprises an electric circuit comprising at least a first sub-circuit and a second sub-circuit: - the first sub-circuit connected to the device for diagnosing the presence of an electric current, the first sub-circuit being adapted to connect in parallel a first section of the first direct current, DC, line to be diagnosed and the terminals (A, B) of the device for diagnosing the presence of an electric current, and - the second sub-circuit connected to the device for diagnosing the presence of an electric current, the second sub-circuit being adapted to connect in parallel a second section of the second direct current, DC, line to be diagnosed and the and the terminals (A, B) of the device for diagnosing the presence of an electric current, - both sub-circuits (10, 11) being electrically connected and the system further comprising: - means for allowing the circulation of the delivered alternating current, AC, through each sub-circuit (10, 11), and - means for preventing the circulation of direct current, DC, between both sub-circuits (10, 11) and towards the device for diagnosing the presence of an electric current, - the first sub-circuit and the second sub-circuit having an impedance, the impedance of each of the sub-circuits (10, 11) being of different value seen from the device for diagnosing the presence of an electric current, and the computing or electronic module being adapted to assess the impedance of the alternating current, AC, delivered to the first and second sections. - a current generator adapted to deliver an alternating current, AC, to said section to be diagnosed, - a first and a second electrical terminals (A, B), and - a computing or electronic module for verifying if the delivered current flows through said section, - the first sub-circuit connected to the device for diagnosing the presence of an electric current, the first sub-circuit being adapted to connect in parallel a first section of the first direct current, DC, line to be diagnosed and the terminals (A, B) of the device for diagnosing the presence of an electric current, and - the second sub-circuit connected to the device for diagnosing the presence of an electric current, the second sub-circuit being adapted to connect in parallel a second section of the second direct current, DC, line to be diagnosed and the and the terminals (A, B) of the device for diagnosing the presence of an electric current, - both sub-circuits (10, 11) being electrically connected and the system further comprising: - means for allowing the circulation of the delivered alternating current, AC, through each sub-circuit (10, 11), and - means for preventing the circulation of direct current, DC, between both sub-circuits (10, 11) and towards the device for diagnosing the presence of an electric current, - means for allowing the circulation of the delivered alternating current, AC, through each sub-circuit (10, 11), and - means for preventing the circulation of direct current, DC, between both sub-circuits (10, 11) and towards the device for diagnosing the presence of an electric current, - the first sub-circuit and the second sub-circuit having an impedance, the impedance of each of the sub-circuits (10, 11) being of different value seen from the device for diagnosing the presence of an electric current, and the computing or electronic module being adapted to assess the impedance of the alternating current, AC, delivered to the first and second sections.