An Integrated Optimal Design Method For Utility Power Distribution Systems

This dissertation presents a comprehensive and integrated design methodology to optimize both the electrical and the economic performance of a utility power distribution system. The proposal is structured to facilitate its adoption and incorporation into the existing utility infrastructure by allowing the various portions of the new design to be implemented gradually into the existing infrastructure without the need to abandon the portions of the existing system that are performing satisfactorily. The topology of the substation plays a vital role in determining both the reliability and the economy of the distribution system. The ring bus topology is offered as the best topology design, and its characteristics as seen at the distribution level are examined. A key concept presented in this dissertation is that the distribution system must be optimized as a whole, not subsystem by subsystem. Optimizing the substation and the primary feeder system separately does not assure an optimal system; in fact, independent design of the two subsystems is likely to produce a non-optimal system laden with operational problems. An integrated approach is essential to assure optimum performance, and the integration process requires an iterative approach. This iterative approach is presented using an example. Innovative changes to the protection strategy of the feeder system can greatly enhance the reliability of the distribution system. The use of communication-based overcurrent detection is presented. This transmission-like scheme, when applied at the distribution level, improves both the reliability and the economy of the system substantially over traditional time-coordinated overcurrent protection philosophies. An application of these proposed innovations leads to the design of a hypothetical system, which is in turn analyzed from both electrical and economic perspectives