Method and photovoltaic inverter for determining the insulation resistance of a photovoltaic system to ground

The invention relates to a method and a photovoltaic inverter (2) for determining the insulation resistance (Riso) of the photovoltaic system (1) to ground (PE). According to the invention, the voltage required for the measurement can be provided in the form of the intermediate circuit voltage (UZK) from the intermediate circuit (6), and the measuring device (13) is designed for actuating an input short-circuit switch (SBoost) for short-circuiting the DC input (3) when the AC separator (8) is open, whereby the intermediate circuit voltage (UZK) can be applied to the DC input (3) in the opposite direction, and the measuring device (13) is designed for detecting a respective measurement voltage (UM1, UM2) with an open and closed switch (Siso) of the voltage divider (14) and for the determining of the insulation resistance (Riso) from the measurement values of the two detected measurement voltages (UM1, UM2) with an open and closed switch (Siso) of the voltage divider (14).