A WORD ABOUT CENTRAL STATIONS.
=170. Central Stations=, as the word implies, are places where, for
example, electricity is generated for the incandescent or arc lights
used in a certain neighborhood; where telephone or telegraph messages
are sent to be resent to some other station; where operators are kept
to switch different lines together, so that those on one line can
talk to those on another, etc., etc. There are many kinds of central
stations, each requiring a large amount of special apparatus to carry
on the work. Fig. 249 gives a hint in regard to the way car lines
get their power from a central power station. As a large part of the
apparatus required in ordinary central stations has already been
described, it is not necessary to go into the details of such stations.
[Illustration: Fig. 249.]
In lighting stations, for example, we have three principal kinds of
apparatus. Boilers produce the steam that runs the steam engines, and
these run the dynamos that give the current. Besides these there are
many other things needed. The electrical energy that goes over the
wires to furnish light, heat, and power, really comes indirectly from
the coal that is used to boil water and convert it into steam. The
various parts of the central station merely aid in this transformation
of energy.
[Illustration: Fig. 250.]
[Illustration: Fig. 251.]
The dynamos are connected to the engines by belts, or they are direct
connected. Figs. 250, 251, show dynamos connected to engines without
belts.
The current from the dynamos is led to large switchboards which contain
switches, voltmeters, ammeters, lightning arresters, and various other
apparatus for the proper control and measurement of the current. From
the switchboard it is allowed to pass through the various street mains,
from which it is finally led to lamps, motors, etc.
Water-power is frequently used to drive the dynamos instead of steam
engines. The water turns some form of water-wheel which is connected
to the dynamos. At Niagara Falls, for example, immense quantities of
current are generated for light, heat, power, and industrial purposes.
[Illustration]