The invention relates to a method for detecting an interruption of an active conductor in an ungrounded direct-voltage power supply system. Five alternative methods are introduced, which are based on determining a current load current, a current total insulation resistance, a current displacement voltage, a current total capacitance or a current total impedance. Each of these methods minimizes the hazard related to accidental touching of two active conductors in an ungrounded direct-voltage power supply system.