Overview

Many involved in power quality have also become involved in distributed generation (DG) because there is considerable overlap in the two technologies. Therefore, it is very appropriate to include a chapter on this topic.

As the name implies, DG uses smaller-sized generators than does the typical central station plant. They are distributed throughout the power system closer to the loads. The term smaller-sized can apply to a wide range of generator sizes. Because this book is primarily concerned with power quality of the primary and secondary distribution system, the discussion of DG will be confined to generator sizes less than 10 MW. Generators larger than this are typically interconnected at transmission voltages where the system is designed to accommodate many generators.

The normal distribution system delivers electric energy through wires from a single source of power to a multitude of loads. Thus, several power quality issues arise when there are multiple sources. Will DG improve the power quality or will it degrade the service end users have come to expect? There are arguments supporting each side of this question, and several of the issues that arise are examined here.

9.1 Resurgence of DG

For more than 7 decades, the norm for the electric power industry in developed nations has been to generate power in large, centralized generating stations and to distribute the power to end users through transformers, transmission lines, and distribution lines. This is often collectively referred to as the "wires" system in DG literature. In essence,...