Fault current analyzer for detecting a fault current and device with fault current detection function

摘要

The invention relates to a fault current analyser (3) for detecting a fault current in an electric network comprising several electric conductors (Ll, L2, L3, N). The inventive analyser comprises a sum current converter (5), whose primary coils consist of the electric conductors (Ll, L2, L3, N) delivering an output signal (UA) on the secondary side and evaluation means (10, 11, 12) connected to the sum current converter (5) for evaluating said output signal (UA). The evaluation means (10, 11, 12) are provided with a filter unit (11) for selecting at least one partial low-frequency signal (ST) of the output signal (UA) and are used for controlling said partial low-frequency signal (ST) when a low-frequency signal limit value (GI) is exceeded and, in the affirmative case, for determining the first short signal sample of the partial low-frequency signal (ST), for determining the effective value of the first short signal sample, for comparing the effective value with a lower and top effective limit value and for deriving a decision whether the fault current exists or not.