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AC Power Systems

10.1 Introduction to Power Systems

10.2 Single- and Three-Phase Systems

10.3 Power Transmission and Distribution

10.4 Learning Objectives

10.5 Practical Application: A Case Study—The Great Blackout of 1965

Problems

Electric power is indispensable for any modern society. Our use and demand for electric power

grows annually at the rate of 2 to 3%; our need nearly doubles about every 25 to 35 years. We, in

the United States, have become so accustomed to reliable and accessible electric power that we

virtually take it for granted.

Even though energy appears in many different forms, the vast majority of all energy delivered

from one point to another across the country is handled by ac power systems. Transporting

electric energy most efficiently from place to place becomes extremely important. Electric power

generation, transmission, distribution, and utilization are the features of any practical power

system.

In the United States power is generated by many generating stations interconnected in an

overall network, known as thepower grid,which spans the entire country. The bulk of the system

is privately owned, whereas a part of the network is owned federally and a part municipally. Some

utility companies in a given geographical area operate aspower poolsfor reasons of economy

and reliability.

The principal source of energy comes from the burning of fossil fuels such as coal and oil

to generate steam, which drives steam turbines, which in turn drive electric generators. Other

important energy sources are hydroelectric and nuclear. In the former, electric generators are

driven by waterwheel (hydraulic) turbines near natural or human-made waterfalls; in the latter,

nuclear reactions generate heat to drive the steam-turbine–generator chain. There are also other

less widely used sources of energy such as geothermal sources, wind, sun, and tides.

In this chapter, to start with, an introduction to power systems will be presented. Then we

analyze three-phase systems, a topic that was covered in part in Chapter 4. Finally, the components

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