An Adequacy Equivalent Approach for Reliability Evaluation of Composite Power Systems

Due to the many complexities involved in the reliability evaluation of even simple networks, power system reliability studies have traditionally been performed in the individual generation, transmission and distribution functional zones. There is, however, a growing interest in adequacy evaluation of composite generation and transmission systems. These analyses provide quantitative information which can be used in the identification of astern weaknesses, comparison of alternate system designs and the justification of new facilities. This thesis is concerned with adequacy evaluation of composite power systems. The basic principles, concepts, pertinent factors and adequacy indices are described and discussed in this thesis. Two practical test systems have been investigated and the results provide further insight into the concepts, pertinent factors, network solution techniques and basic adequacy indices presented. The computation time required to investigate the required number of credible outage events or contingencies for a large composite power system can be a major obstacle in system adequacy evaluation. An adequacy equivalent approach is presented in this thesis to study the adequacy performance of a selected area (Area of Interest) in a power network in which the remaining network (Interconnected Area) is modeled as an equivalent. This is a practical way to perform detailed adequacy analysis in a selected region of a large composite power system, with a reasonable computation time. It is particularly useful when sensitivity analysis is to be conducted in the Area of Interest or in conducting adequacy studies of interconnected areas where one area can be replaced by an equivalent, thus reducing the size of the overall system. A simple radial configuration is utilized to illustrate the basic technique for developing feasible adequacy equivalent models in the Interconnected Area (IA) and for implementing adequacy evaluation in the Area of Interest (AI) using the developed equivalent. The concepts have been applied to the analysis of the two test systems. Adequacy assessments using the adequacy equivalent approach and by solving the entire network show that the adequacy equivalent method provides reasonably accurate reliability indices with a greatly reduced computation time