A method and a device for safely switching a direct-voltage system, in particular a photovoltaic system, in the event of an arc occurring on a direct-current side. Wherein the generated direct current and the produced direct voltage are set with regard to power guidance. In the event of a sensor-detected arc, the power guidance is adjusted and a power change of the arc is detected. In the event of a power drop of the arc, a serial or parallel arc is detected according to the adjustment direction of the power guidance. In the event of a serial arc a direct-current interruption is produced, and in the event of a parallel arc a short-circuit current is produced.