Abstract: The invention relates to a differential protective system for electric power transmission paths where measurement quantities obtained from the currents at either end of the section to be monitored are digitized and subjected to digital sine filtering. Sign signals are obtained from auxiliary measured quantities generated from the filtered current measurement values and taken to both ends of the section to be monitored for evaluation with the generation of an exciting signal. To make the system largely unaffected by frequency variations in the currents, further filtered current measurement values are obtained by cosine filtering; from those values and from the individual filtered current measurement values, a measurement quantity is generated by absolute value generation and low-pass filtering. This measurement quantity causes a further exciting quantity to be established using an absolute value comparison quantity. If both exciting signals are present, the sign signals are evaluated.