be monitored and a basically random predeterminable reference location x z r which as a practical matter however lies within the conductor or line section including x 0 and x x e to be monitored the fault or defect location x z which is to be ascertained for instance to be localized at a position falling within or without the aforementioned conductor section according to the prevailing assumptions possesses the characteristic that at the time t there is identically true the following wherein the symbol u represents the conductor voltage u the symbol i the conductor current i and the symbol i l the short circuit current i l at the fault location by means of a 34 wave voltage 34 u w r w i x t introduced for the sake of simplicity and the real wave resistance r w there now can be defined a first wave function a x t and a second wave function b x t by the following equation 3 equ1 with the inductance l 39 per unit length and the capacitance c 39 per unit length for the boundary conditions according to equation 1 with uniform wave travel time u03b1 u221a l 39 c 39 and after substitution in the wave function equations 2 results in the following the first wave function thus constitutes a voltage wave moving towards the right the second wave function a voltage wave moving towards the left and the latter while taking into account the sign can be conceptually considered as the wave of the first wave function traveling towards the right which is reflected at the fault location for the fault location x z there is correspondingly plausible a coordinate shift as a function of time for the.