cting, it is
obvious that the perfection of control attained in some of our modern
plants is not their least characteristic.

[Sidenote: _Switching
Apparatus_]

The switch used for the 11,000 volt circuits is so constructed that
the circuits are made and broken under oil, the switch being
electrically operated. Two complete and independent sets of bus bars
are used, and the connections are such that each alternator and each
feeder may be connected to either of these sets of bus bars at the
will of the operator. From alternators to bus bars the current passes,
first, through the alternator switch, and then alternatively through
one or the other of two selector switches which are connected,
respectively, to the two sets of bus bars.

[Illustration: INSIDE WALL OF TUNNEL SHOWING 64 DUCTS]

Provision is made for an ultimate total of twelve sub-stations, to
each of which as many as eight feeders may be installed if the
development of the company's business should require that number. But
eight sub-stations are required at present, and to some of these not
more than three feeders each are necessary. The aggregate number of
feeders installed for the initial operation of the subway system is
thirty-four.

Each feeder circuit is provided with a type H-oil switch arranged to
be open and closed at will by the operator, and also to open
automatically in the case of abnormal flow of current through the
feeder. The feeders are arranged in groups, each group being supplied
from a set of auxiliary bus bars, which in turn receives its supply
from one or the other of the two sets of main bus bars; means for
selection being provided as in the case of the alternator circuits by
a pair of selector switches, in this case designated as group
switches. The diagram on page 93 illustrates the essential
features of the organization and connections of the 11,000 volt
circuits in the power house.

[Illustration: MANHOLES IN SIDE WALL OF SUBWAY]

Any and every switch can be opened or closed at will by the operator
standing at the control board described. The alternator switches are
provided also with automatic overload and reversed current relays, and
the feeder switches, as above mentioned, are provided with automatic
overload relays. These overload relays have a time attachment which
can be set to open the switch at the expiration of a predetermined
time ranging from .3 of a second to 5 seconds.

[Illustration: CONVERTER FLOOR PLAN
SU