DETECTION OF GROUND FAULTS IN ENERGY SUPPLY NETWORKS WITH A COMPENSATED STAR POINT

The invention relates to a method for detecting a ground fault in an electric energy supply network (10) with a compensated star point. Measurement values which characterize a state of the energy supply network (10) are detected at at least one measurement point of the energy supply network (10); a zero-sequence voltage and an admittance variable are ascertained from the measurement values; and the zero-sequence voltage and the admittance variable are used to detect the ground fault in the energy supply network (10). The aim of the invention is to increase the reliability of a ground fault detection in particular even in the event of a high-ohm ground fault. This is achieved in that the star point of the energy supply network (10) is temporarily connected to ground by activating a grounding device (13) in the presence of measurement values which indicate a ground fault in the energy supply network (10), and a ground fault is detected in the energy supply network (10) if the zero-sequence voltage exceeds a specified zero-sequence voltage threshold and the admittance variable exceeds a specified admittance threshold while the grounding device (13) is activated, the activation of the grounding device (13) causing a reduction of the zero-sequence voltage threshold. The invention also relates to a protection device (16a-c) for carrying out such a method and to a corresponding protection system.