A DI-circuit breaker device includes a summation current converter for detecting fault currents in a phase conductor and a neutral conductor, and a detection device for detecting fault states of a protective ground conductor. The detection device detects the presence of a phase voltage on the protective ground conductor as a fault state. The detection device has a capacitive sensor which, when touched by a user, forms an electric capacitor with an impedance relative to ground potential. The detection device further has evaluating electronics adapted to determine a phase position by connecting the sensor to the phase conductor and, separately therefrom, to the neutral conductor. The evaluating electronics determine the absence of a phase voltage on the protective ground conductor when there is no voltage between the neutral conductor and the protective ground conductor when phase is present at the phase conductor. Further, a corresponding operating method is described.