An apparatus is provided for monitoring a high-voltage on-board power supply system of an electrically operated vehicle for the occurrence of overloading, wherein the high-voltage on-board power supply system includes as components one or more energy sources and/or one or more energy sinks which are each connected via a conductor line arrangement to a first supply potential line and to a second supply potential line. Each of the components is assigned a current sensor which is designed to detect a current flowing through the respective component and to transmit information representing the level of the current to an evaluation unit for evaluation. The evaluation unit is designed to compare the current with a first current threshold and a second current threshold and to output a switch-off signal at least for the component assigned to the current sensor if, as a first criterion, the level of the current and the duration of the level of the current are between the first and second current thresholds.