n.

CHAPTER VII

LIGHTING SYSTEM FOR PASSENGER STATIONS AND TUNNEL

In the initial preparation of plans, and more than a year before the
accident which occurred in the subway system of Paris in August, 1903,
the engineers of the Interborough Company realized the importance of
maintaining lights in the subway independent of any temporary
interruption of the power used for lighting the cars, and, in
preparing their plans, they provided for lighting the subway
throughout its length from a source independent of the main power
supply. For this purpose three 1,250-kilowatt alternators
direct-driven by steam turbines are installed in the power house, from
which point a system of primary cables, transformers and secondary
conductors convey current to the incandescent lamps used solely to
light the subway. The alternators are of the three-phase type, making
1,200 revolutions per minute and delivering current at a frequency of
60 cycles per second at a potential of 11,000 volts. In the boiler
plant and system of steam piping installed in connection with these
turbine-driven units, provision is made for separation of the steam
supply from the general supply for the 5,000 kilowatt units and for
furnishing the steam for the turbine units through either of two
alternative lines of pipe.

The 11,000-volt primary current is conveyed through paper insulated
lead-sheathed cables to transformers, located in fireproof
compartments adjacent to the platforms of the passenger stations.
These transformers deliver current to two separate systems of
secondary wiring, one of which is supplied at a potential of 120 volts
and the other at 600 volts.

The general lighting of the passenger station platforms is effected by
incandescent lamps supplied from the 120-volt secondary wiring
circuits, while the lighting of the subway sections between adjacent
stations is accomplished by incandescent lamps connected in series
groups of five each and connected to the 600-volt lighting circuits.
Recognizing the fact that in view of the precautions taken it is
probable that interruptions of the alternating current lighting
service will be infrequent, the possibility of such interruption is
nevertheless provided for by installing upon the stairways leading to
passenger station platforms, at the ticket booths and over the tracks
in front of the platforms, a number of lamps which are connected to
the contact rail circuit. This will provide light suff