This case study deals with the determination of single phase fault in distribution networks with 10 kV and 20 kV voltage levels based on voltage and current signal during transient process. There are certain difficulties when determining single phase fault in medium voltage distribution networks with respect to the fault location in transmission networks. Distribution networks include numerous branches which lead to ambiguous indication of the fault, conductor are non-uniform, there are numerous distributed loads and higher resistance fault values are evident. An approach, which would ensure the fault calculation in networks, without regard to the neutral point treatment, was looked for. This fault location calculation was carried out in the filed of low- and high-frequency transient phenomena. By means of single phase fault computer simulations different parameters are used for the model distribution output and the frequencies, where charge redistribution during the first milliseconds after the fault occurs, are separated. The dependence of the neutral point treatment frequency spectrum, initial current and voltage phase shift, fault resistance, fault location and distributed load dynamics have been observed. The procedure for an approximate frequency calculation of charge transients has been given, as well. Fault location calculation, based on low frequency transients, depends significantly on fault resistance and this method cannot be applied in the case of high impedance faults. During this study, the method for single phase fault location based on voltage travelling waves was developed. The calculation according to this method does not depend on fault location resistance, non-uniformity, load dynamics and the influence of distributed sources. The influence of non-uniform conductors was eliminated by means of corrected distances for the spreading of travelling wave speed. To apply the travelling wave method, sampling frequency of at least 1 MHz is required for voltage input signals.