7745 Germantown Avenue, Philadelphia PA 19118
© Jane Mork Gibson, Workshop
of the World (Oliver Evans Press,
1990).
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.