Circuit arrangement and method for monitoring electrical isolation

A circuit arrangement (16) for monitoring electrical isolation in a power supply system (7) which electrical isolation is provided between a high-voltage system (8) and a low-voltage system (9) of the power supply system (7), wherein the high-voltage system (8) and the low-voltage system (9) are connected to ground (14), and wherein the high-voltage system (8) has a first connection (T+) for a first supply voltage potential and a second connection (T−) for a second supply voltage potential of a voltage source (10), characterized in that in each case at least one variable resistor (Rm1, Rm2) is connected between the connections (T+, T−) and ground (14), and in that a voltage measuring device (17) for detecting a potential shift of the ground (14) relative to the supply voltage potentials when at least one of the resistors (Rm1, Rm2) is varied and an evaluation device, which determines the ability of the electrical isolation to function depending on the detected potential shifts, are provided.