7745 Germantown Avenue, Philadelphia PA 19118
© Jane Mork Gibson, Workshop
of the World (Oliver Evans Press,
The Chestnut Hill Substation
was built in 1914 to serve the expanding needs of the
area. The Philadelphia Electric Company had added a
fourth generating station in 1913 as an expansion of the
Schuylkill River Christian Street Station in anticipation
of growth, especially for traction and railroads. In
addition, the use of electricity in homes was becoming
more and more popular, and Philadelphia Electric Company
could service the area best with a substation having
transformers to step down the alternating current (a.c.)
power from the high voltage necessary to transmit
electricity from the generating station into the low
voltage required in dwellings and most businesses.
The original machinery has been removed from the substation, and state-of-the art equipment was installed in the 1960s. The present electrical installations at the substation change 13,000-volt to 400-volt electricity, and the voltage is stepped down further to 240 and 120 volts at transformers located at the top of telephone poles throughout the community before the electricity is finally distributed for use.
At the eastern end of the substation three transformers receive the power via underground lines from Cedarbrook Station on Ivy Hill Road in Mount Airy. The power is then transmitted over three main bus lines to feeders and then passes through circuit breakers (to prevent overloads), reactors (to lower the current if necessary), and regulators (with two disconnects per regulator line) before leaving the building in underground distribution circuits that feed electricity to most of Chestnut Hill. There are ten circuits in operation, and there is space for eight more, which will probably never be added. The substation was planned with future expansion in mind, but technical improvements in equipment have made it possible to increase the output without physical expansion.
Safety precautions have been taken throughout the installation. Besides the safeguards of the circuit breakers and the disconnects, a bank of batteries (130 volts total) is kept charged to take over operation of the circuit breakers in an emergency and then permit gradual resumption of power to reduce the possibility of overload when going on line. The transformers are cooled by the self-contained circulation of oil, which in turn is cooled in large radiators. There is a high pressure water sprinkler system installed to spray the individual transformers in case of overheating. 1
The building was designed by John T. Windrim, the Philadelphia Electric Company's architect and a member of the board. Windrim, together with engineer W.C.L. Eglin, designed several monumental electric generating stations: Schuylkill Station (1903), Chester Station (1918), Delaware Station (1920) and Richmond Station (1925). The Chestnut Hill Substation is a one-story, brick Georgian Revival building with recessed openings, cut stone surrounds, center entrance on the north facade, dentil cornice, parapet and flat roof. 2
1 Information obtained from tour of site and interview with Frank Casper, September 1, 1989.
2 J.M. Moak (compiler), "Inventory of Buildings Within the Chestnut Hill District...," March 14, 1985.
Update May 2007 (by Jane Mork Gibson):
Philadelphia Electric Company is now PECO Energy. The building appears to be the same, providing the same service.