Circuit breaker device (SG) for a low-voltage circuit, comprising in a housing (GEH): - input-side first conductor connections (EL) for the low-voltage circuit, which are connected to output-side second conductor connections (AL) via a series circuit composed of an isolating contact system (KS) and a semiconductor switch (HL), - a drive (AT) and a handle (HB) for the isolating contact system (KS), which handle is accessible on the housing, - a display unit (AE) and an operating unit on the housing (GEH), - a current sensor (SEN), which determines the level of the current of the low-voltage circuit, - a control unit (ST), which is connected to the current sensor (SEN), the display unit (AE), the operating unit, the drive (AT) of the isolating contact system (KS) and the semiconductor switch (HL), characterized in that the isolating contact system has an isolating property, wherein the control unit (ST) is configured in such a way that: - in a switch-on process, first the isolating contact system (KS) is closed and then the semiconductor switch (HL) becomes low-impedance, - in a manual first switch-off process, the semiconductor switch (HL) becomes high-impedance and the isolating contact system (KS) remains closed, - in the case of a determined current that exceeds a first current threshold value for a first time period, according to the first switch-off process, the semiconductor switch (HL) becomes high-impedance and the isolating contact system (KS) remains closed, - in the case of a determined current that exceeds a second current threshold value for a second time period, for a second switch-off process, the semiconductor switch (HL) becomes high-impedance and then the isolating contact system (KS) is opened, - in the case of a determined current that exceeds a third current threshold value, according to the second switch-off process, the semiconductor switch (HL) becomes high-impedance and then the isolating contact system (KS) is opened. - input-side first conductor connections (EL) for the low-voltage circuit, which are connected to output-side second conductor connections (AL) via a series circuit composed of an isolating contact system (KS) and a semiconductor switch (HL), - a drive (AT) and a handle (HB) for the isolating contact system (KS), which handle is accessible on the housing, - a display unit (AE) and an operating unit on the housing (GEH), - a current sensor (SEN), which determines the level of the current of the low-voltage circuit, - a control unit (ST), which is connected to the current sensor (SEN), the display unit (AE), the operating unit, the drive (AT) of the isolating contact system (KS) and the semiconductor switch (HL), characterized in that the isolating contact system has an isolating property, wherein the control unit (ST) is configured in such a way that: - in a switch-on process, first the isolating contact system (KS) is closed and then the semiconductor switch (HL) becomes low-impedance, - in a manual first switch-off process, the semiconductor switch (HL) becomes high-impedance and the isolating contact system (KS) remains closed, - in the case of a determined current that exceeds a first current threshold value for a first time period, according to the first switch-off process, the semiconductor switch (HL) becomes high-impedance and the isolating contact system (KS) remains closed, - in the case of a determined current that exceeds a second current threshold value for a second time period, for a second switch-off process, the semiconductor switch (HL) becomes high-impedance and then the isolating contact system (KS) is opened, - in the case of a determined current that exceeds a third current threshold value, according to the second switch-off process, the semiconductor switch (HL) becomes high-impedance and then the isolating contact system (KS) is opened. <EOS>