The present monograph is dedicated to the subject of numerical methods for modelling of asymmetrical modes of operation of power systems. The scientific novelty of the monograph mainly pertains to numerical methods for calculation of power system regime parameters with multiple asymmetrical faults and the method for calculation of power system fault transients which combines the numerical inverse Laplace transformation and topological modelling of the power system in Laplace space. This study also includes multiple examples of both fault and preparatory calculations with their respective implementations in computer codes and basic analysis of the characteristics of different faults as well as potential operation of relay protection for some of the examples. The theoretical background, practical examples and additional information provided in this study will prove useful not only to students but also to engineers and researchers already working in the field of relay-based protection and automation.