We have identified the characteristics of power engineering facilities as an object which may be damaged in case of emergency situations, as well as the special aspects of modelling this process. The degree of protection has been defined with respect to the power engineering facility. We have created the general structure of the degree of protection of power engineering facilities from the influence of adverse factors in emergency situations and the hierarchy of submodels (models of technical systems, elements and adverse factors). We have proved the methodological principles of analysis of the safe conditions of the power engineering facility and have chosen the optimal mathematical tool for describing the destructive effect. We have created the criteria of the degree of protection of technical systems of the power engineering facility and its elements; the condition of probability of survival and notion of a weak element. We have developed the general algorithm of the estimation procedure of degree of protection of the power engineering facility from adverse factors in emergency situations.