Device for feeding in electrical energy of a number of strings of photovoltaic modules in an electricity network

The device (1) has a connection terminal (7) comprising an over-current protection unit that includes a power switch (9) for selectively disconnecting strings (2). A central insulation monitoring unit (15) detects an insulation status of the strings. The power switch is opened and closed by controllers (11-13) via a motor in response to the insulation status provided by the central insulation monitoring unit to select and disconnect one of the strings having an insulation failure. The power switch is designed for double open-circuit voltage of the strings.