CHAPTER 5 - POWER GENERATION AND DISTRIBUTION

As a Construction Electrician first class, you may have the responsibility of supervising the installation, maintenance, and repair of mobile electrical power (MEP) equipment. This equipment is portable and ranges. in size from 5 kilowatts to 100 kilowatts. In time of war or national emergency, advanced base functional components (ABFC) will normally be used at temporary overseas bases. Even in peacetime, MEP equipment may be used at remote bases.

At large, more permanent activities, you may have duties associated with the installation and operation of large electrical power systems.

A power distribution system includes all parts of an electrical system between the power source and the customer's service entrance. The power source may be either a local generating plant or a high-voltage transmission line feeding a substation that reduces the high voltage to a voltage suitable for local distribution. At most advanced bases, the source of power will be generators connected directly to the load.

This chapter gives the correct procedures for the operation and maintenance of power plants and distribution systems and presents technical information for the selection and installation of power-generating plants.

POWER GENERATION

The characteristics built into naval electrical installations are simplicity, ruggedness, reliability, and flexibility to permit continued service after a part of the equipment has been damaged. It is the function of those who operate these plants to make full use of their inherent capabilities and to maintain, as far as possible, uninterrupted availability of electrical power where it is needed.

To be able to do this, operating personnel should possess the following:

A thorough knowledge of how to operate and maintain the components of the electrical plant

A complete familiarity with the electrical plant as a whole

A comprehensive understanding of system operation

The ability to apply general electrical and electronic principles to specific installations

A knowledge of a few simple rules of system operation that are applicable to all naval installations

When you have finished studying this chapter, see if your capabilities for performing the above functions haven't improved.

GENERATOR SELECTION

When an overseas base is first established, electrical power is needed in a hurry; you will not have time to set up a centrally located generating station. Instead, you will spot a portable plant at each important location requiring power. Table 5-1

Table 5-1.\Types of Portable Generators

G-Gasoline driven. D-Diesel driven.

*-Panel connections permit, at rated kW output: 120/208V

3-phase 4-wire, 120V 3-phase 3-wire, 120V single-phase

2-wire, 120/240V single-phase 3-wire.

lists some of the standard alternating current (ac) generators available. These standard generators are capable of meeting the power requirements of advanced bases. Representative 30-kilowatt and 200-kilowatt generators are shown in figures 5-1 and 5-2.

The electrical loads to be supplied-power, voltage, phase, frequency, and duty cycle requirements-govern the selection of generating equipment. Probable load deviation, probable life of the installation, availability of fuels, and availability of skilled personnel are other important factors.

Electrical plants at advanced bases serve a varied load of lighting, heating, and power equipment, most of which demand power day and night. The annual load factor (the ratio of average power to peak power) of a well-operated active base should be 50 percent or more with a power factor (explained later in this chapter) of 80 percent or higher. If the load is more than a few hundred feet from the power source, a highvoltage distribution system is required.

If several generators are to serve primary distribution systems, they should generate the same voltage to avoid the need for voltage transformation. The number of phases required by the load may differ from that produced by the generator. As loads can usually be divided and balanced between phases, most generators of appreciable size are wound for three-phase operation.

Figure 5-1.\30-kW portable generator.