Direct-current switching device

A method for switching off a direct current, which comprises the steps of:

• switching-off a switching unit thus resulting in a generation of an arc, a resonant circuit being excited by an arc voltage occurring at the arc and an oscillating resonant current being generated which is superimposed on the direct current still flowing through a first switching unit during a switching off process, thus forming a superposition current;
• switching off the superposition current at a zero crossing of the superposition current, and energy stored in the resonant circuit being dissipated by an arrester;
• providing the switching unit with a series circuit of a first switching unit and a second switching unit whose switching behavior differs from that of the first switching unit, and the superposition current flowing through the series circuit of the first and second switching units is switched off at the zero crossing by the second switching unit;
• providing a delay device which, when the direct current is switched off, opens the second switching unit at a time after the first switching unit;
• providing a drive driving both the first and second switching units;
• and
• providing the delay device with a gearing mechanism being connected between the second switching unit and the drive, a duration of delay of the delay device and a natural frequency of the resonant circuit are matched to one another such that a switching off of the second switching unit does not start until an amplitude of the oscillating resonant current has a value of at least 75% of the direct current that is to be switched off, and/or until after a period of time that is at least three times the natural frequency of said resonant circuit.