Abstract: In order to locate a cable fault in a cable, a testing apparatus applies a test signal to the cable so as to induce an electrical oscillation. The testing apparatus includes a voltage source that generates the test signal, which e.g. ignites an electrical arc at the cable fault or applies a voltage surge to the cable, to cause the electrical oscillation. The apparatus further includes a measured signal evaluation device to measure the resulting oscillations in the time domain or the frequency domain, and carry out a spectral analysis in the frequency domain, so as to automatically determine the location of the fault preferably from the total phase rotation of the signal, the phase rotation of the reflection at the first cable end, the phase rotation of the reflection at the cable fault, and the imaginary part of the propagation constant of the signal in the cable.