DETECTION DIRECTIONNELLE D'UN DEFAUT A LA TERRE AVEC UN SEUL CAPTEUR

The device (20) has a processing module (26) processing a signal representative of zero sequence current (Io) of a line of a multi-phase network. A fault detection device (28) activates the module based on a detection signal of occurrence of earth fault (D) in the network. An interpretation unit (36) interprets processing results of the signal to determine whether the fault is in upstream of the device. The module comprises a counting unit (32) to determine a number (N) of zero crossings of the signal on preset duration and a comparison unit (34) to compare the crossings with a threshold (Z). Independent claims are also included for the following: (1) a protection relay comprising a fault flow indicator (2) a method for directional detection of earth fault in a multi-phase network (3) a method for protecting current line during occurrence of earth fault.