Elements of the AC Power System

The process of generating, distributing, and controlling the large amounts of power required for a municipality or geographic area is highly complex. However, each system, regardless of its complexity, is composed of the same basic elements with the same basic goal: Deliver ac power where it is needed by customers. The

primary elements of an ac power system can be divided into the following general areas of

technology:

• Power transformers
• Power generators
• Capacitors
• Transmission circuits
• Control and switching systems, including voltage regulators, protection devices,and fault isolation devices

The path that electrical power takes to end-users begins at a power plant, where electricity is generated by one of several means and is then stepped-up to a high voltage (500 kV is common) for transmission on high-tension lines. Step-down transformers reduce the voltage to levels appropriate for local distribution and evenual use by customers. Figure 1.7 shows how these elements interconnect to provide ac power to consumers.