CHAPTER 3
ELECTRICAL DISTRIBUTION
SYSTEMS
distribution system to be distributed to the various
Almost every function undertaken aboard a naval
electrical loads throughout the ship.
ship depends upon electric power for its
accomplishment. From the launching of missiles against
The ac power distribution system aboard ship is
an aggressive force to baking bread for lunch, electric
made up of the following parts:
power is vital to a ship's ability to accomplish its
AC power plant
mission.
Switchboards that distribute the power
LEARNING OBJECTIVES
The equipment that consumes the power
Upon completion of this chapter, you should be able
The ac power distribution system consists of the
to do the following:
following three parts:
1. Identify the various electrical distribution
1. The service power distribution system
systems installed on board Navy ships.
2. The emergency power distribution system
2. Identify the characteristics and construction
3. The casualty power distribution system
features of and recognize the operation of ac
generators.
ELECTRICAL DISTRIBUTION
3. I d e n t i f y s o m e w o r k i n g p r i n c i p l e s ,
SYSTEM
characteristics, and design features of
The electrical distribution system is the link
between the ship's source of electrical power and the
4. Recognize several factors that determine the
ship's electrical loads. Power is normally supplied from
output voltage and frequency of ac generators.
the ship's own generators but can be supplied from an
5. Identify various operating fundamentals of
external source through the shore power cables. In
ship's service distribution systems, including
naval ships, most ac power distribution systems are
switchboards, bus transfer equipment, and
450-volt, three-phase, 60-Hz, three-wire systems.
shore power.
Bus ties interconnect the ship's service generator
6. Recognize various principles and procedures in
and distribution switchboards. Therefore, any
rigging or unrigging casualty power.
switchboard can be connected to feed power from the
generators to one or more of the other switchboards
7. Recognize distinct maintenance and test
allowing the generators to operate in parallel. In large
procedures used in keeping an electric plant on
installations (fig. 3-1), power from the generators goes
the line.
through distribution switchboards or switchgear groups
to the load centers, through distribution panels, and on
AC POWER DISTRIBUTION
to the loads. Distribution may also be direct from the
SYSTEM
load centers to some loads.
On some large ships, such as aircraft carriers, a
The ship's service electric plant is that equipment
system of zone control of the ship's service and
that takes the mechanical power of a prime mover and
emergency power distribution system is provided. The
converts it into electrical energy. The prime mover may
system sets up several vertical zones that contain one or
be steam, gas turbine, diesel, or motor driven. The
more load center switchboards supplied through bus
mechanical energy of the prime mover is converted into
feeders from the ship's service switchgear group. A load
electrical energy in the ship's service generators. These
center switchboard supplies power to the electrical loads
generator sets supply power to the ships ac power
3-1
