Calculation of voltages and currents in the point of protection during faults

This work consists of two major parts - theoretical and practical. The theoretical part describes the course of short-circuit current in time, its components, characteristic values, and various types of short-circuits that may occur in electrification network. The theoretical part also describes the method of symmetrical components, its principles, fundamental relations and its use for handling the short-circuit current in electrification network, especially the asymmetrical short-circuits. The last theoretical section following the method of symmetrical components shows a summary of formulas used to calculate substitute short-circuit impedances in various elements of electrification network. The practical part then tries to answer how to handle short-circuit currents in a given network using the method of symmetrical components. Calculation is made for each type of short-circuit that may occur in the network, and voltage and current ratios are given for the point of short-circuit as well as for the point of a distance protection; main evaluated parameter of calculation is a short-circuit impedance measured by the distance protection. The conclusion of the practical part specifies why a compensation of distance protection is needed in ground short-circuits