guard against erdschlussfehlern high bestaendigkeit.

摘要

Protection device for high resistance ground faults in a power network the fault detection principle of which is based on an indirect study of non-harmonic frequency components of the phase currents. When such a fault has occurred, a considerable change of the energy contents of these frequency current components arises. This change can be detected by the device according to the invention. If by comparison (4e) between digitized input signals (I min ) and a harmonic Fourier model (4d) of the same signals, i.e. generation of the residuals of the system, it is found that a difference exists, and if the corresponding loss function VN (4f) for a certain time exceeds a lower limit value - all on condition that a zero sequence current (IO) exists - then the device indicates a high resistance ground fault on any of the phases of the network.