In the article an algorithm of structural analysis of schematic and operational peculiarities of electric power systems intended for definin g problem areas in a power system is suggested. The algorithm is based on searching for electric grid elements, which emergency tripping results in inadmissible variations of steady state parameters. Calculations are performed in normal and repair schemes. An example of the algorithm application for the analysis of schematic and operational conditions of 110 kV electric grid of Saint-Petersburg is given.