as petroleum and paint.
The high
the frequency is changed, usually from
noise level of generators may be
25 to 60 cycles or vice versa.
another factor in their location.
c. Converter substation.
In the
14. SUBSTATIONS
converter
substation,
current
is
changed from alternating to direct
The use of substations is required
current.
when
high-voltage
systems
are
15. TRANSFORMERS
employed.
The
purpose
of
the
substation
is
to
change
the
alternating current received from the
A transformer is the apparatus used
generating
plant
to
the
voltage,
to make changes in voltage, either up
frequency,
and
type
of
current
or down.
The voltages required for
required by the distribution system.
long distance transmission are greater
There
are
three
main
types
of
than those that can be generated and a
substations.
transformer is used to step up the
voltage.
The voltage required to
a. Transformer substation.
In a
operate motors and lights is less than
transformer
substation,
the
high
that required for distribution and a
voltage from the generating plant is
transformer must be used to step down
stepped down to a lower voltage which
the voltage.
A transformer receives
can
be
used
by
the
distribution
electrical energy from one circuit and
system.
There is no change in
transfers
it
to
another
circuit
frequency and the current of the lower
by magnetic action.
The circuit from
voltage is still alternating current.
which energy is received is called the
This is the most common type of
primary circuit, the receiving circuit
substation and is usually what is
is the secondary circuit.
Usually
meant when speaking of a substation.
the primary and secondary circuits
are
at
different
voltages.
An
b. Frequency-changer
substation.
elementary transformer consists of a
In the frequency-changer
substation,
primary
and
a
secondary
coil
surrounding an iron core. Alternating
Figure 9.
Transformer taps on primary.
1-14
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