LESSON 2
ELECTRICAL DISTRIBUTION SYSTEMS
TEXT ASSIGNMENT -------------------- Attached memorandum.
MATERIALS REQUIRED ----------------- None.
LESSON OBJECTIVE ------------------- To teach you how to design simple
electrical distribution systems
for theaters of operations.
ATTACHED MEMORANDUM
1.
INTRODUCTION
transmission.
Also, the plant must
produce enough voltage to transmit the
An
electric
power
system
power from the plant to the services.
fundamentally
consists
of
an
To
simplify,
the
longer
the
electrical source connected by wires
transmission distance, the higher the
to an electrical load.
The number of
required voltage.
For example, to
loads is then increased to as many
transmit
power
over
a
75-mile
buildings, shops, and warehouses as
distance, the generating plant should
must be supplied.
In a low voltage
produce 88,000 volts.
For a 10-mile
system, the generator may be of the
distance, only about 13,000 volts are
small portable type and the distances
required. Now, it is obvious that the
to the loads may be as high as 1,500
services cannot utilize electric power
feet. The design of these low-voltage
at such high voltages.
Remember that
systems is based on the magnitude and
common household voltages range from
location of the loads.
Existing
120 to 240 volts.
Here is where the
electric power systems will not be as
other components of the system come
simple
as
that
explained
above,
into use.
That part of the system
especially when transmission of power
beyond
the
stepdown
is
made
over
long
distances
for
substation
is
designated
as
the
relatively high power loads. Figure 1
distribution system.
shows a typical high-voltage electric
2.
DISTRIBUTION SYSTEM LAYOUT
power system.
This type of system
serves a large number of loads or
services that are usually located at a
There
are
two
general
methods
great distance from the generating
of
arranging
a
distribution
plant; that is, up to 50 or 75 miles.
system;
that
is,
the
layout
of
The generating plant must produce
the wires to the various facilities
enough power (kilowatts) to supply the
entire
load
plus
the
power
lost
through
wire
in
2-1
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