Substations of the Broad Street Subway of Philadelphia

The Broad Street subway is the first step of a system of underground high-speed railways which is being designed and built by the City of Philadelphia. This paper describes the substations which furnish power for traction at 630 volts direct current and for the subway lighting and signals at 4,600 volts, 60 cycles. The first section of the Broad Street subway required three substations which were equipped with synchronous converters and completed in 1928. Later, when the subway was extended, a fourth substation was added, but by this time so much progress had been made in the design of substation apparatus, particularly in respect to increasing the current capacity of mercury arc rectifiers and perfecting iron-clad high-voltage switching equipment, that a radically new design of substation was decided upon embodying these types of apparatus. This substation was placed in operation this year. This paper contains a description of the apparatus and method of operation provided in both types of substations and indicates the advantages of the equipment selected. Much thought was also given to special operating features for safety and reliability.