Abstract: A process and system for the purpose of running and controlling electrical high-voltage power lines, particularly of the pertinent generators, wherein a line identification is required with the determination of the longitudinal equivalent reactance of each line section coupled with a measuring point or with a generator connected there, the generator being represented by this longitudinal reactance between the measuring point and a point on the line with amplitude and phase-rigid line voltage. The reactance is determined continuously from the local measured dimensions (P, Q, V.sub.1) by using a majority of predetermined values (X.sub.e1 -X.sub.e3) of the searched for reactance through similarity comparison of the time developents of phase angle differences (d.sub.1 to d.sub.3) formed by the predetermined values (X.sub.e1 -X.sub.e3) and the local phase angle (d.sub.m).