Edison Hart Electrical Power Substation, Detroit Michigan
The Detroit Edison Hart Substation is typical of the kind of electrical substations built for the Detroit Edison Company in the early 20th century to step down (reduce) high voltage incoming electric current before distribution to residential lines and industrial customers; original equipment also converted incoming alternating current into direct current for streetcar lines.
The Detroit Edison Hart Substation is a two-story, steel and reinforced-concrete structure located on the southwest corner of the intersection of East Vernor and Hart on the far east side of Detroit. The building is approximately 43 feet in height. Basically rectangular in shape, the substation measures 167 feet long on the west and 84 feet wide along Vernor. However, a small section of the rectangle (25' x 35') is missing from the southeast corner of the building; therefore, the principal facade along Hart—representing the original 1914 construction--is only 130 feet in length.
The exterior of the substation is sheathed in brown-colored brick. Ornamentation is confined to the Hart and Vernor facades. A thick horizontal band made of white stone divides the base from the buildings main body. Basement-level windows still remain on the Hart facade; those along Vernor were replaced with brick in the early 1940s. The body of the substation extends over both stories. It consists of a series of 13.5 foot wide bays: six along Hart and four on Vernor (of which the western most was part of the 1928-29 addition). Bays are framed by sections of brick, each inlaid with a pair of vertical shafts of white stone which create the impression of columns that begin at the base and rise to support the repeating brick-made arches located just below the cornice line. Before the 1940s, the large recessed brick panels at the center of the bays contained multiple-pane windows (the bottom halves consisted of four panels which opened to the inside). The stone window ledges were left intact. The remaining upper sets of windows--two panels on each swing outward--are from the original installation. At intervals the green-painted concrete cornice features a pair of brackets which appear to support the widely overhanging eaves. A streamlined stone-coped parapet rises over the cornice along the Hart and Vernor facades. Alterations in the 1940s led to the levelling off of the corners of the original parapet, as well as to the rebuilding of the staircase and reconstruction of the area surrounding the main front door at the northeast corner of the structure. The elaborately bracketed and scrolled entrance was removed, replaced with brick, and a single steel door installed. The wooden door at the southeast corner remains unaltered.
The southern facade is a massive brick construction, uneventful except for a small lone window located in the middle. The rear of the building is similarly functional in design. All eight of the transformer rooms are serviced by wooden doors which allow for the removal and installation of machinery. Ventilation for the transformer rooms is provided by panel openings and hoods in the doors and by rectangular vents located just above the doors. All of the windows in the building assist in drawing off heat produced by the substation's machinery, as do two long rows of wind-activated turbines located on the roof.
The interior of the Hart Substation includes three levels: a basement about 9 feet deep through which electrical cables enter and leave the building; and two stories above ground. Walls either are made of brick or concrete; floors, ceilings, and the roof are made of concrete. The single largest space in the building is the machine room: it measures 40 feet wide, 160 feet long at its greatest extension, and reaches from the floor to the roof. A large overhead crane with a capacity of 50,000 pounds can travel most of the length of the machine room. Built around 1915 by the Northern Engineering Works of Detroit, the overhead crane originally facilitated maintenance of three motor-generator sets which produced direct current for the local streetcar system. Arranged in a single row beneath the second story balcony overhang is the principle extant equipment in this room: the original marble panels upon which rest volt meters, watt/hour meters to record usage, fuses, mechanical circuit breakers, and other control and monitoring devices. Many of the meters are original. An operator's office and two phone booths stand at the northern end of the machine room.
The Hart Substation includes a mixture of equipment of different vintages, with relatively little of the original installation still intact. The circuit breakers located on the first floor between the machine and transformer rooms, for example, are solenoid-operated Westinghouse Type B-26 oil-filled breakers, rated at 600 Amps at 7,500 volts, but they in fact operated at 4,800 volts. The latest patent date on the nameplate is 1925.
Eight pairs of transformers and voltage regulators are situated on the west side of the building on the ground floor. There are eight Ferranti Packard Transformers, Class OW, rated at 10,000 KVA, 3 Phase, all built in 1970 in Toronto, Canada. These are paired with eight Westinghouse induction type voltage regulators, rated at 6,000 KVA, 3 Phase, at 4,800 volts. This type of voltage regulator features a motor-driven shiftable "rotor" coil which shifts to achieve optimum inductive coupling. These voltage regulators may well be the original equipment, since the last patent date shown on the nameplate is 1915. They are capable of varying the output voltage plus or minus 10%. Voltage adjustment was needed to match shifting load throughout the day or week.
In addition, there are seven Westinghouse induction type voltage regulators, Type D, rated at 300 KVA, 3 Phase, 4,800 volts, located on the second level of the substation. These can handle a secondary current of 720 amps at 220 volts (5% regulation) or 360 amps at 480 volts (10% regulation). The last patent date for these regulators is 1928. The two sets of voltage regulators worked in tandem; the main, large ones "pre-setting" the voltage to each of the eight 4,800 volt main circuits and the smaller ones further regulating the branch circuits.