The Electrical Aspects of Cogeneration System Design

Cogeneration and the reasons that it is a viable industry today are discussed. Both bottoming and topping cycles may be employed for cogeneration; however, the topping cycle is the major focus of current cogeneration projects due to its applicability in large cogeneration power plants. The effect and reasons for the Public Utility Regulatory Policies Act removal of many of the disincentives of cogeneration are discussed. The relative efficiencies of conventional and combined-cycle cogeneration power plants are compared in a typical example of a large cogeneration power plant currently under construction. Many considerations face the electrical engineer in the design of a cogeneration power plant. Many applications will be found in industrial plants and will utilize industrial thinking within the plant; however, many decisions will be influenced by conventional electric utility thinking, due to the interface with the electric utility in the switchyard. Basic discussion of the considerations required of the electrical engineer, including electrical system arrangement, integration of the new generation into the plant electrical system, short-circuit matters, one-line diagrams, generator characteristics, excitation systems, step-up transformer ratings and characteristics, auxiliary transformers (station service), distribution systems, and system grounding, is given for preliminary guidance in design.