Reliability evaluation of bulk power systems using analytical and equivalent approaches
Electric power systems throughout the world are undergoing considerable changes due to the converging forces of deregulation, technological revolution and evolving customer expectations. Quantitative reliability evaluation plays an important role in the development, design and operation of composite generation and transmission or bulk power systems. This thesis presents research conducted on the development and examination of concepts, techniques and pertinent factors in the reliability evaluation of composite power systems using direct analytical and equivalent analytical approaches. A major difficulty in composite system reliability evaluation using analytical methods is the long computation times required to investigate the extremely large number of possible system outage events in an actual composite system. Only the credible system states are usually investigated. The credible system states are those that make significant contributions to the reliability indices and are usually determined by considering outages up to a certain level. The computation time increases rapidly with increase in system size and the defined outage level. The obtained adequacy indices can often be inaccurate due to limited depth of analysis. Computation times can be significantly reduced when the unchanging portion of a system can be replaced by a reduced equivalent reliability model. Equivalents can prove very useful in the evaluation of large systems where sensitivity studies are to be performed on a portion of the system or when the system is to be interconnected to a further system, which is to be studied in detail. Reliability equivalent concepts also have many other applications in composite system evaluation. This thesis illustrates the foundations, evaluation procedures, pertinent factors, reliability indices and computer program design concepts associated with composite system evaluation using the analytical approach. The thesis presents three advanced algorithms which effectively improve the accuracy of the reliability indices without considerably increasing the required computation time. The three advanced algorithms are illustrated using numerical examples and are applied to the evaluation of two reliability test systems. The thesis provides a complete description of adequacy equivalent concepts and their applications in composite system evaluation. System studies on two reliability test systems and interconnected forms of the two reliability test systems using the equivalent techniques are provided. The concepts of reliability cost/benefit analysis and the utilization in this area of the equivalent techniques and the new algorithm for annual adequacy indices are presented in this thesis.