Method for detection of a ground fault, which occurs in the vicinity of a neutral point in an electrical device, as well as an apparatus for carrying out the method

The invention relates to a method for detection of a ground fault (18), which occurs in the vicinity of a neutral point (22), in a polyphase electrical device which is operated at a fundamental frequency, in particular an electrical machine (10) or a transformer which has a number of windings (11, 12, 13), which are associated with the individual phases, one end of each of which windings (11, 12, 13) is connected to the neutral point (22) and the other end of each of which windings (11, 12, 13) is connected directly to a power supply network via a power supply system connection (14, 15, 16). Simple and reliable detection is achieved in that the change in the physical variables which is associated with a ground fault (18) is measured in the immediate vicinity of the ground fault (18), and is evaluated.