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Full text of "The history and development of the Pratt Street Power Plant of the Baltimore Consolidated Gas Electric Light and Power Company"

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The deplorable condition of city transportation in Bal- 
timore "before 1899 came about due to competition among the many 
existing lines. On tarda 4, 1899 these independent companies 
joined hands and became the United Railways & Electric Company. To 
supply electrical energy for the street cars, the numerous small 
generating plants sere dispersed and a large power plant was es- 
tablished on Pratt Street, 

The Pratt Street rower riant was brought to completion 
shortly after the Baltimore fire of 1904. As an engineering pro- 
ject it attracted much attention, because of a radical departure 
from general power practice. The station occupied a space 132' by 
490' and consists of three buildings, known as Engine House no. 1, 
Boiler House, and Engine House No. 2 located in the order named 
from Pratt Street. The equipment Included four engines of 3000 H. P. 
each, directly connected to generators of 2000 kilowatt capacity. 
The engines were driven by a battery of thirty-two "boilers anc. the 
main engine room was equipped with an overhead electric crane, 
the largest in the world at that time. 

Each year as the smaller plants were abandoned the Pratt 
Street Plant Increased 'its capacity until in 1909 the capacity 
of the station was 39,000 kilowatts and the only other power 
plant in operation was at Bay Shore Park, In 19H the United Rail- 
ways & Electric Go. signed a contract for additional hydro-electric 
power from the Kc Call Ferry Plant of the Pennsylvania Water & 
Power Co. This amount being supplied by the Pennsylvania Co. was 
gradually Increased until the Pratt Street Station was operated 
for emergency service at power failures of the Pennsylvania Co. 

On January 12, 1921 the power equipment of the United 
Railways passed into the ownership of the Baltimore Consolidated 
Gas Electric Light & Power Co., an affiliate of the Pennyslvania 
Co., with the agreement that the Railways Co. would buy all of its 
power for the next fifty years from the Consolidated Co. 

The Pratt Street Power Plant was used to handle the 
energy required for the United Railways and due to increased load 
conditions new equipment was found necessary. In 1926 a new switch 
house was built inside of the old Engine Room No.l of the Pratt 
Street Plant, The old engines were removed and a large portion 
of the Engine Room remodelled and turned into a storage room. At 
the present time besides generating and handling electrical 
energy, the station also engages in the supplying of steam for 
heating purposes, 

Although the lest port and the Gould Street Power Plants 
are superior to the Pratt Street Power Plant, it may be said that 
the Pratt Street Ststion is the heart of a great railway system. 
Through this station pulsates the very life blood of the trolley 
lines of Baltimore, the current that energizes the motors of a 
thousand cars. 


A view of Baltimore taken from an old book clearly shows 
the large power plant located on Pratt Street. This building is 
the most prominent on the picture and is dlstinquished by four 
hugh stacks. 



The grievous condition of city transportation in Balti- 
more before 1899 was the result of competition among the numerous 
transit companies then in existence. On Larch 4, 1899 these inde- 
pendent organizations were consolidated into the United Railways 
& Electric Company. This merger made possible the centralization 
of power equipment, and, therefore, the supplying of cars with 
electrical energy most economically. Losses In long cables when 
carrying direct current were reduced by using alternating current 
at high voltages, with the final conversion into direct current 
for the street cars at substations. 

Since the United Railways & Electric Company was formed 
as e combination of many independent, self-supporting companies, 
it acquired numerous power plants in different parts of Baltimore, 
The wastefulness of continuing under such an arrangement soon 
became apparent. This was due to the fact that the combined capa- 
cities of the small plants was greater than the maximum load of 
all lines at any time. A much better arrangement being a single 
unit of enough capacity to supply the entire demand. 

The United Railways & Electric Company then proceeded to 
build a central power station and to gradually do away with the 
numerous smaller plants. The erection of this generating station, 
£nown as the Pratt Street Power Plant, was the completion of an 
adequate and reliable electric car service in Baltimore. 



One of the familiar sights along Baltimore's water- 
front is the old Pratt Street Power Station, with its massive 
stacks and lofty conveyor towers. This structure was brought to 
completion, shortly after the Baltimore fire of 1904, by the 
United Railways & Electric Company as a main generating station 
for its motive power and to supplant the numerous smaller gener- 
ating stations throughout the city. The Pratt Street Power House 
was built when the whole task of generating current for this city 1 s 
railways was bourne by the systems power stations. It was the scene 
of constant activity, and Its immense engines labored day and night 
unceasingly in manufacturing electricity which was served out to 
the many lines of street railways. 

This power station is located on the South side of Pratt 
Street, on pier No. 4. The station occupies a space 132' by 490' 
and consists of three buildings, known as Engine House No. 1, Boiler 
House, and Engine House No. 2, located in the order named from 
Pratt Street. All three buildings rest on pilings, superimposed 
by a concrete mat varying in thickness from three to eight feet,' 
and are of standard steel framing enclosed by curtain walls of 
red brick with terra-cotta trimmings. These buildings are of fire 
proof construction throughout, the roofs being of slag or slate, 
the floors of reinforced concrete, and all windows, doors and trim 
of steel or hollow metal construction. 

All main generating units were operating condensing. The 
condenai ter was taken from the slip on the west side of the 
station. A complete system of concrete intake and discharge wells 
was provided for this purpose. The condensers of all engine driven 


units were of the Worthlngton Barometric type, while the circula- 
ting outfits, with the exception of the five 2000 kilowatt units 
located in Engine House No. 2, which were motor driven, were either 
turbo or engine driven. The 5000 kilowatt Curtis Turbine was fitted 
with a Worthlngton Jet Condenser, while the 7. estinghouse Parsons 
Turbine was fitted with two Wo. 18 V-estinghouse Le Blanc condensers 
with turbo driven air and circulating pumps. 

Excitation current was provided by one 150 kilowatt 
motor driven unit, one 150 Itllowatt engine driven unit, one 200 
kilowatt engine driven unit and one 300 kilowatt turbine driven unit, 

Steam was supplied by thirty- two Babcock and ttllcox water 
tube boilers fitted with Roney stokers. The boilers were arranged 
so that there were sixteen located on each floor of the boiler 
house. The boiler house was fitted with four, steel, brick-lined, 
self-supporting stacks, eight boilers being connected to each 
stack by individual smoke flues. The stacks were each thirteen 

t in diameter and one hundred and ninety- two feet high. Installed 
In each stack was a Schutte & Koerting blast nozzle to provide 
additional draft for emergency conditions. 

Coal was delivered to the pier in scows and elevated a 
distance of one hundred and thirty feet by means of two Hunt 
electrically operated coal towers to the weighing platforms where 
the coal, after being crushed, was weighed and distributed to the 
storage bunkers oy means of two Hunt gravity return railways. 
Mechanical sampling machinery, located on the weighing platform, 
automatically took a sample of each lot and delivered it to a 
pulverizing machine from whence it was fed into sampling cans In 

A view of the plant showing the four huge stacks atop 
the Boiler House. The structure at the upper left consists of 
the conveyor system and the coal towers. 

One of the conveyor cranes raising coal from a scow 
to the coal tower. As can be seen from the picture, the scow 
can be brought alongside the power plant. 


the proper condition for analysis. 

The storage bunkers were made of steel and concrete 
construction, each of 2000 tons capacity, located above the second 
floor of the boiler room. From the bunkers the coal was conveyed 
directly to the boilers by means of an elaborate system of coal 
chutes and spreaders. 

The ashes were dumped from the ash hoopers under the 
boilers into two Hunt bucket conveyors. They were then elevated 
and dumped into concrete storage bins, located outside the boiler 
room on the coal tower structure, at a sufficient height to admit 
of the ashes being loaded directly into cars and hauled away. 

Engine Room No.l was provided with a fifty ton traveling 
bridge crane, and fitted with an auxiliary ten ton Snolst. This crane 
was electrically operated and was the largest crane, of this type, 
in the world. Engine Room No. 2 was fitted with a thirty ton 
crane of the same type. 


The switching control for the entire station was located 
in Engine Room No. 1, the direct current board being separated 
from that of the alternating current board. The alternating current 
switching gear was in a separate structure located in the northerly 
end of Engine Room No.l. The switching structure proper was twenty- 
five feet wide by eighty- five feet long, three stories and a 
basement in height, and was separated from the engine room proper 
by a brick wall. All feeders, both outgoing and incoming, ended in 
the basement, and their series transformers were located in compart- 
ments in the up going branches. The first floor held bus bars, feeder 


oil switches and leads from alternators with their series trans- 
formers. On the second floor w<:-re located the alternator bus bars 
and oil switches, while the third floor was devoted to the switch- 
ing and control hoards in the operation of all high tension appar- 
atus, as well as of the exciter, field and auxiliary systems. The 
fourth floor is used for office and storage battery room. A perma- 
nent grounding system was run throughout the switchboard structure, 
having receptacles at various points to recieve flexible lead3 for 
grounding transformer cases, switch bases, all buses, oil switch 
pots and feeder cables. 

The alternating current high tension control bench was 
built in a semi-circular form and was In twenty-two sections. 
Black: marine- finished slate was used for the panel work and was 
supported by structural steel framework. One section of the con- 
trol bench was fitted with standard testing instruments. On every 
bench containing ammeters, voltmeters and other instruments there 
were plug receptacles connected to buses running to testing instru- 
ments so arranged that by means of plugs, any instrument could be 
connected to the standard instruments for comparison. The test 
instruments provided for were voltmeter, ammeter, power factor 
meter, indicating wattmeter, recording wattmeter and frequency meter. 

The exciter switchboard was loc&ted on the control floor, 
opposite to and facing the curved benchboard. There were ten black 
marine- finished slate panels, provided with a full complement of 
apparatus especially arranged to control all exciter, field and 
lighting circuits. These circuits operated at 110 volts, as did also 
the alternating current instrument circuits, so that no current of 


a higher potential than 110 volts was brought to the control floor. 

The hue bar and oil switch structure was built of light- 
colored shale brick, with concrete slabs, poured as the structure 
was made. 

A comprehensive system of pipes and ducts was installed 
for the reception of cables, the main feature of which was the com- 
plete isolation of each group of cables belonging to a machine unit 
and the installation of each cable in a separate conduit. Provision 
was also made in this structure for the receipt of current from the 
hydro- electric plant of the Pennsylvania ".ater & Power Co. located 
on the Susquehanna River at Holtwood x'a. , a distance of approximate- 
ly fokrty miles from the city. 

A high tension potential transformer, for testing pur- 
poses, was installed on the basement or cable floor, with its leads 
connected to bus bars along the whole length of the ceiling. This 
transformer was of 150 kilowatt capacity with a capacity of 333 
kilowatt for a minute or more. With it the voltage could be steadi- 
ly raised from 3000 to 30,000 volts, 

Three direct current machines were used to take care of 
the load in the immediate center of the city. The balance of the 
load, with the exception of two lines, one northwest and the other 
southeast of the city, which were provided for by two small direct 
current steam stations, was taken care of by five substations lo- 
cated at various advantageous points throughout Baltimore. Current 
was transmitted to the substations from the Pratt Street Generating 
Station at 13,200 volts by means of fokrty miles of No. 0000, 3- 
conductor, and thirteen miles of No. 0, 3- conductor, paper insula- 


ted, lead encased copper cable. 

The proceeding material concerning the equipment, con- 
struction and methods of operation of the Pratt Street Power 
Plant clearly shows the extent to which the United Railways & 
Electric Company went to obtain an efficient and economical 
power supply for the city of Baltimore. This power plant truly 
represented a remarkable advancement in the engineering world. 



The power system of the United Railways & Electric Com- 
pany was neither built overnight nor was this system completed with 
the erection of the Pratt Street Power Plant. Instead, this plan 
required years to complete and consisted of transfering all gen- 
erating apparatus of the small stations to the <-. ntral power plant. 

In 1904, the transit system consisted of the following 
power plants and their corresponding capacities: Pratt Street, 
15,600 kilowatts j Falls Road, 2,250 kilowatts; Light Street, 2000 
kilowatts; Bear Creek, 675 kilowatts; Carey Street, 600 kilowatts; 
Gilmore Street, 550 kilowatts; and Back River, 424 kilowatts. The 
power system at this time represented a total capacity of 23,849 
kilowatts. The capacities of substations then In use were; Druid 
Hill, 4,500 kilowatts; Dugan' s Wharf on Pratt Street, 3,000 kilo- 
watts; and Nunnery Lane, 1,500 kilowatts. 

With the completion of the Northern substation, and the 
transfer of two additional units to the Pratt Street Power Plant 
from abandoned plants, It became possible to shut down the plants 
at Gilmore Street, Light Street, Bear Creek, Carey Street and 
Preston Street, Each of these plants having been generating electri- 
city at a cost greatly In excess of thst at Pratt Street. 

In 1907 the Bay Shore power house was constructed to sup- 
ply light and power for Bay Shore Park, It having been found more 
satisfactory to build the Bay Shore Station, using equipment that 
was idle, than to run feeders from the Eastern Substation, This 
was the last power plant built by the United Railways & Llectric 
Company, and its 1,175 kilowatt capacity was overshadowed by the 
25,000 kilowatt capacity of the Pratt Street Power Plant. 


In 1908, due to damage by fire, it was found necessary 
to abandon the Falls Road Plant. Calles were run from this plant 
to the Northern Substation where the additional load was taken care 
of by increasing the output at Pratt Street. 

The year 1909 found the Pratt Street Power Plant busy 
with activity and in its golden era. The capacity of the plant 
had now reached a total of 39,4-00 kilowatts and it was the only 
power plant in operation, with the exception of Eay Shore, A plant 
at the Owings Mills Station was kept in operating condition, but was 
not used. 

Thus, in less than ten years the power supply system of 
the United Railways & Electric Company had changed from an extra- 
vagant system of numerous small operating plants tda modern cen- 
tralized power combination. At this time, plans were made for supply- 
ing additional power from the Lc Call Ferry Plant of the Pennsylvania 
Water & Power Company by running high tension cables from this com- 
pany to the Pratt Street Station. The first contract for additional 
power was signed in 1911. In that year the United Co. purchased 
45 1 175,000 kilowatt hours from the Pennsylvania Company, and gener- 
ated 63,003,722 kilowatt hours at their Pratt Street Plant. This 
amount of additional power being supplied was gradually increased 
until the Pratt Street Station was used solely for emergency ser- 
vice at power failures of the Pennsylvania Water 3c Power Company, 


On January 12, 1921 the United Railways & Electric Com- 
pany, the Consolidated Gas, Electric Light & Power Company of Balti- 
more and the Pennsylvania Water & Power Company entered into an 


agreement covering the sale of the Pratt Street Power Plant to the 
Consolidated Company and the purchase of power from this company 
"by the Railways Company. This agreement provided for a payment 
of four million dollars for the power station and for increased 
power supply by the Pennsylvania Company to the Consolidated 
Company as required. The Hallway Company in the future will devote 
its time exclusively to traction operations. Under a perpetual 
contract , with flexible terms adjusted to meet changing conditions, 
It will purchase all electrical energy needed for the operation 
of its lines during the next fifty years from the Consolidated Com- 
pany, Thus, the United Railways & Electric Company left the gener- 
ation of electricity to a company specializing in electric power 

The main idea of this purchase and contract was, of course, 
to gain the many advantages and economies Incident to the consoli- 
dation of all electric generating plants under a single management » 
The savings possible under such a unified system of power generation 
were very substantial, for Instance; At that time there was suffl- ^c, 
cient steam generating equipment at Westport, the main generating 
plant of the Gas & Electric Company, to supply all necessary steam 
generation for the railway company as well as its own load for 
several years to come, when used in connection with all the hydro- 
electric energy sent to Baltimore from the Susquehanna River. This 
situation made possible the shutting down of the Pratt Street Station 
for some time, which resulted In large economies from the saving in 
labor at one point and the saving in operating cost due to the 
larger and more efficient units available at Westport. 


As in the case of all sound business transactions, this 
agreement was favorable for all parties concerned. The employees 
of the Cons olid s ted Gas ± Electric Company felt gratified that 
their company was rapidly growing as a wholesale power manufac- 
turing concern, while the United Railways & Electric Company was 
gratified that their resources and opportunities to extend the 
railway system were greatly Increased. 


For several years the Pratt Street Power xlant was idle, 
but later on it was again used to supply power to the United 
Railways & Electric Company. The electrical equipment located at 
Pratt Street was found inadequate to handle the energy required 
by the Railways Company, As it was necessary to provide new 
switching equipment, it was also necessary to provide a suitable 
building to properly arrange and house this equipment in a most 
efficient manner, For this reason a new switch house was constructed, 

'rhe new switch house consisted of a five story steel and 
concrete building, constructed just inside the old Engine Room 
No, 1 and along its w«st wall. The west wall of the old building 
was used as part of th^ new structure, while a new east wall, new 
floors and a roof was required. The window and door openings were 
alt' e red to meet new conditions; some were bricked up while In 
others glass was replaced with sheet copper and permanent louvres, 
installed for ventilating purposes. The basement of the new build- 
ing was approximately at the same level as the street pavement 
along Pratt Street, so a new doorway was provided in the north wall 
near the northwest corner of the bull . This aew doorway was 


treated to architecturally match the old doorway near the east 
wall. The "basement consisted principally of cable trenches and 
facilities for the incoming and outgoing high tension cables. 

The main floor and first gallery contained concrete 
bus structures of similar design to those in the latest sub- 
stations of the company. The second or reactance floor, directly 
above the first gallery, contains the reactors, while the top 
floor was fitted out as an operating room, operator's office and 
relay repair department. The "building also has an electric ele- 
vator located at the north end of the structure and runs from the 
basement to the top floor. 

In order to obtain safety in switching there was pro- 
vided new high powered switches with a rupturing capacity of 
20,000 amperes. This was a great improvement over the old type 
"C M switches which had a rupturing capacity of only 2,000 amperes, 
while the short circuit currents that may be expected on the 13,200 
volt system is approximately 20,000 amperes. Reactance colls were 
also supplied on each feeder from Highlandtown and nest port, which 
limited the short circuit current on any of these feeders to 10,000 
amperes or less. This meant that no matter what happened to one of 
these cables the oil switches could easily open the circuit doing 
something less than one-half of the work for which they were guar- 

Considerable study was also given to the proper handling 
of the cables from the street duct lines on Pratt Street into the 
basement of the new switch house. With the old arrangement there 
had been much congestion, so additional lines were built and many 
of the old cables were rerouted. The cables were completely segre- 

One of the main control panels located in the new 
switch house. The instruments at the top of the panel are am- 
meters while those at the "bottom are overload time relays. 
The bus "bars, which are controlled by this panel, are three 
phase, 13,200 volts and run to various substations throughout 
the city. 


The generator panel containing instruments that read 
kilowatts, kilowatt- hours, power factor and field current. All 
instruments on the main panel and the generator panel were made 
by Westinghouse. 


gated into three groups belonging to the United Railways & Electric 
Company, Pennsylvania Water & Power Company and the Baltimore 
Consolidated Gas Electric Light & .tower Company. 

Upon completion of the new switch house in 1927, all 
equipment in the old switch house was abandoned. This space was 
found to make an ideal record store room which was badly needed. 
Therefore, the store room was relocated from Spring Gardens and now 
occupies the old Engine Room No. 1. 

In 1927, a large section of Baltimore was being served 
by the District Steam Heating System. This system consisted of 
supplying steam to office buildings, department stores and res- 
taurants, for heating purposes. In 1928 the Consolidated Gas Elec- 
tric Light & Power Company took over the district steam operations, 
and since that time five hundred privately owned boiler plants have 
been displaced by this clean and efficient heating service. 

As shown by the diagrams on page fourteen this system 
is supplied by three steam plants, namely, the Pratt Street Power 
Plant which supplies high pressure steam, the Terminal Plant which 
supplies low pressure steam, and the Block Plant which receives 
the return condensed steam. There is also shown on page fourteen 
the cross-section of one of the main conduits used to carry the 
steam from these plants to various advantageous points in the 
downtown section of Baltimore. 

Today one finds the old Pratt Street Power Plant still 
serving Baltimore to the best 01 its advantage. Power In the form 
of steam being used for heat and comfort while electricity x^ 
provided for the rapid transport cation 01 t-1 people throughout 


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The wholesale adoption of electric power "by the manu- 
facturing and transportation companies of America, and their use of 
central station equipment, read like the story of the automobile. 
In fact, these two great services of mankind, electrical energy and 
gasoline vehicle, have experienced much the same phenomlnal growth, 
and yet a growth which has so entwined these forces into the very 
economic being of the nation that they will endure as long as the 
nation Itself, 

The power system set up in Baltimore by the United 
Railways & Electric Co., known today as the Baltimore Transit Co., 
and the Baltimore Consolidated Gas Electric Light & rower Co. 
would have "been a credit to any community and it is without a 
doubt one of the most important factors in the growth of that 
city. Since the rratt Street ^ower Plant was the very soul of this 
power system, it may be said that this power station was one of 
the greatest steps ever made by Baltimore to attain fame and 
glory as a modern American city. 

Well known to the average layman are facts concerning 
the electric lights In his home, the street car he rides to work 
on, and possibly the steam that heats his office, but so seldom 
does he realize Just exactly what is behind all these wonderful 
conveniences. The answer is, of course, the power plant, Perhaps 
It will take some dreary morning when the current Is shut off 
to awaken the public to the full realization of the important part 
that the modern power plant plays in their lives. Then, when Mr, 
John Q. Public awakes to find he Is without electric lights, has 
to walk to his place of employment and work in a cold office, 


wlll he finally realize that there is something quite Important 
about a main power station. 

I mention this "because I found so many well educated 
persons, living in Baltimore, had not even heard of the Pratt 
Street Power riant. 


Mr. E. S. Baiiey--Chief operator of the Pratt Street Power Plant, 

Mr. Raymond Tompkias — The Baltimore Transit Co. 

Mr. H. C. Bell — Operator 

Mr* Long — Operator 

Mr. H.M. Rood— Electrical engineer of Allen Bradley Co. 

Baltimore Gas & Electric News. 

The United Railways Forum, Vol. 1. 

Electrical WOrld, 

Baltimore Gas & Electric Co. Yearbook 1921-1937.