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Adequacy Equivalents in Composite Power Systems

Date

1987-09

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Degree Level

Doctoral

Abstract

In a modern society, load shedding and poor quality of power supply have severe economic and social consequences. There is little disagreement among the suppliers, the users, and the regulatory agencies that providing an adequate supply of electric power is of prime importance. Adequacy evaluation of a composite power network relates to the examination of both generation and transmission facilities required to satisfy the demand at the bulk customer load points. Most power utilities use deterministic methods to conduct adequacy studies on their systems. The drawback of these methods is that they are not responsive to many of the parameters which actually influence system adequacy. There is, however, a growing interest in the power industry in using probabilistic methods as they provide more realistic results with regard to the identification of system weaknesses, comparison of alternative system designs, and the justification of new facilities. This thesis is concerned with the adequacy evaluation of composite power networks using probabilistic methods. It extends the state of the art and provides insight into adequacy evaluation of both moderate sized and large power systems by evaluation, analysis and solution of some specific problem areas. The pertinent factors such as the consideration of high level independent outages, station originated and common cause outages, and corrective actions taken under an outage event, affect the calculation of adequacy indices for a power system. These factors are identified and their effects are illustrated using three test systems. The adequacy indices calculated for a network do not provide absolute measures regarding the performance of the network and these indices should be interpreted in conjunction with the factors involved in arriving at their values. The adequacy indices reported in this thesis are obtained by solving a network using the network flow method and the A.C. load flow method. The differences in the indices for the standard IEEE Reliability Test System (RTS) resulting from using these solution techniques at various load levels are discussed. The computation time required to calculate adequacy indices considering all credible outages in a large power network can be very large. In this thesis, two new approaches that can be used to conduct a number of adequacy studies in a small area of interest (AI) of a large power system are described. The first approach considers outages only in a part of a network that affect to a great extent the adequacy performance of the AI. The second approach determines the adequacy of the AI after developing an adequacy equivalent for the remaining part of the network. This approach can also be used to consider further higher level outages in a network. The application of each method under various situations is illustrated for the three test systems and their interconnected networks. The weaknesses and the strengths of each technique are also discussed. It is expected that the proposed methods will provide a good framework for power utilities when studying the adequacy of their systems.

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Degree

Doctor of Philosophy (Ph.D.)

Department

Electrical Engineering

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