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Full text of "History and construction of northern substation of the Baltimore Transit Company / by Elies Elvove."

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file:///X|/Special%20Collections/purgatory/Phi%20Mu/Eleove,%20Elise/blueprint.txt[4/12/2011 11:23:01AM] 



HISTORY AMD CONSTRUCTION 
OF THE 
M ORTHERN 3UB3T AT ION 
OF TuE 
BALTIMORE TRANSIT COMPANY 



by 
Eliea Elvove 



A Paper Prepared as a Requirement for Initiation 

for 
TAU BETA PI 
1938 



duWIAHY 

In the expansion of public utilities, the public 
is generally only acquainted with that part of the service 
which affects it most directly. The basic functioning of 
the industry is of the greatest importance to the public 
but is usually unnoticed* 

The development of the street car has been made 
possible , not only by research, but by developments in 
economical power systems. .Public utilities are inherently 
best able to serve their customers when unhampered by com- 
petition; they are monopoly industries, u.'he chaotic con- 
dition of city transportation in Baltimore prior to 1899 
was the result of competition among the many existing lines; 
the consolidation of these independent organizations into 
the United Railways and Electric uompany on „aareh 4, 1899 
was the beginning of one of the best transit organizations 
in this country, to supply the cars with electrical ener- 
gy most economically called for centralization of power 
equipment; the merger made this work possible. Losses 
in long cables when carrying direct current were reduced 
by the use. of alternating current at high voltages, with 
the subsequent conversion into direct current for the trol- 
leys at substations* The final abolition of all genera- 
ting plants in favor of wholesale purchase of power from 
the Baltimore uonsolidated ij-as and electric Company was 
to be expected in the line of increased economy. 



-ii- 



Northern substation is not unusual; it is neither 
the first substation constructed nor is it the latest; it 
is not the largest plant and is not the smallest; its true 
importance lies in the fact that it marked a step forward 
in the development of an efficient, economical and depend- 
able transit organization. 

Northern substation was built on narford Avenue 
at Holy Cross lane to strengthen the lines in the northern 
section of the system; intended as a 4000 KW plant, the origin- 
al building, now known as number one house, was completed 
early in 1905 but did not begin operating under full load 
until July 7, 1906. The station was found inadequate as 
soon as it began operatingj and an additional building, now 
known as number two house, was constructed in 1907. The 
second structure was a three-walled building built upon 
the north wall of the original house and in it two 1500 
KW rotary converters were originally installed and operation 
began in the fall of 19u7. The total capacity of the station 
at this time, therefore, was 7000 KW. 

Converter wo. 7, a c-000 KW unit was placed in op- 
eration June 15, 1912 because of an increased load expected 
from the Democratic national Convention, which convened in 
Baltimore that year. An eighth unit, the largest in the 
plant, having a capacity of 3000 rJi, was installed to take 
care of additional increase of load in the northeastern 
section of the city; this converter began operation in 
November, 1918. 



-Ill 



To avoid power losses in the long lines leading from 
Northern to the Hamilton section, it was decided to build a 
semi-automatic substation in that section, in is station was 
designed to be operated by one man, wording only part-time, 
and capable of being removed from operation by switches at 
the northern substation, This station was completed in 
September, 1929; of the two rotaries installed there, one 
is a &QQQ KW unit removed from northern, and the other is 
a 1125 rotary removed from Uentral substation. 

Thus Substation .Number 4, northern, now has a 
rotary converter capacity of 10,000 tvW and operates twen- 
ty-one and one half hours every day. .uever since its con- 
struction has there been a total shutdown of the plant while 
scheduled for operation. The continual, monotonous hum of 
the converters heard by passers-by seems to indicate de- 
pendability and power. "Street car service must be main- 
tained" they whine. 



The History and (Jonstruction of the northern Sub- 
station of the rialtimore Transit Company. 

Progress in industry has been so tremendous in 
the past century that it is hard to comprehend the vast 
amount of capital involved in the continual improvement of 
methods of operation. This is especially true in those in- 
dustries commonly known as public utilities, in this cate- 
gory are included organizations serving the public . with 
water, gas and electric supply, transportation, and com- 
munication—services vital to the general populace. The 
public demands dependable, economical and efficient service 
from the utilities, and in order to comply with this demand, 
they have continually had to expand and improve their plants. 
Improvements in equipment and methods of operation have con- 
tinually been utilized. 

Many advancements in service have escaped the no- 
tice of the public; publicity is given only to that equipment 
which most closely affects the customer, many examples of this 
could be cited: the streamlining of locomotives, air condi- 
tioning of ears, and improvements in sleeping cars have been 
widely advertised nihil e equally Important developments in 
signal equipment, driving machinery, and ■ "velvet" rails 
have escaped notice, oimilarly, the public has been made to 
notice the new Presidents* Conference uomittee cars by wide- 
spread advertisement. However, there is a great difference 



/ 



-2- 



in the mere passing of one of the new cars through the streets 
and the extensive mechanical, supervisory, and power factors 
that stand back of that car. 

The history of the street car of today is more or 
less well known; numerous papers have been written on the 
subject. Baltimore has had a leading part in this develop- 
ment; this city saw the first commercially operated electric 
street car in the world make its maiden run from Oak and 
Twenty-fifth otreets to the woodbury terminus on August 10, 
1885. This car operated on a third rail system and the 
locomotive and car are illustrated in iigure 1. The line 
operating this trolley car was the iiampden branch of the 
Baltimore Union Passenger uailway, a horse- car line. 

In spite of the successfulness of this demon- 
stration, the transit industry was still skeptical of 
electric power as a means of propulsion and on May 23, 
1891, the first cable-car line in Baltimore began operation 
on Druid Hill Avenue. This type of road was operated by 
means of an endless steel cable running on sheaves within 
conduits constructed between the rails; a gripping device 
held the cable at the "gripman's" will and moved the coach 
forward. This car was doomed to a short life because of 
numerous cable i'ractures and improvements in electrical 
propulsion equipment and much capital invested in such roads 
was lost. Figure 2 illustrates such a car. 

To the casual observer, this history of the street 



-3- 




T^ird-raH Daft ipotor a^d passenger trailer 
Baltimore -& Hairjpdej) Eailwa/ 



Figure 1. 




Irip car of typical cable liye 



Figure 2. 



-4- 



oar itself is a history of the transit industry; however, 
the important factor of power supply nas had an important 
effect on the growth of the industry. Developments in 
power supply to the trolleys should be included in any 
history of electrical transportation. 

POWER SUPPLY DEVELOPMENT 

FroflJ the time of the first electric railway line in 
Baltimore to 1899 many independent lines were built in the 
city, iach of these systems suppled its own power from 
steam-operated generation stations located in strategic po- 
sitions along the lines. The combined capacities of these 
plants was greater than the maximum demand at any time of 
all the lines; a single generation station of smaller capa- 
city could have supplied the entire load at much greater 
economy. The advantages of joint control of such an industry 
soon became apparent and on March 4, 1899 a merger of all 
Baltimore companies was accomplished. The new organization 
was Known as the United railways and electric Company. 

oince united was formed as a combination of sev- 
eral independent, self-supporting companies, it possessed 
numerous power plants in various parts of the city. The 
wastefKUV/iess of such an arrangement soon became apparent. 

United immediately began the centralization of 
equipment to a central power plant with auxilliarles as needed. 






-5- 



The inefficiency of transmitting direct current over long 
lines to outlying sections was obvious and it was decided 
to generate power as alternating current in the central 
station and subsequently convert this to direct current 
for the trolleys in converter substations to be located 
in strategic parts of th* city. 

A large power plant located on .Pratt Street was 
enlarged and altered to act as the central power station. 
In line with the development of transmitting power as 
alternating current at nif/f voltages, the first converter 
substation was constructed on uruid Hill avenue in 1903, 
This was followed in short order by substations at .Nun- 
nery Lane and at the main generating station on Pratt 
street. 

Thus in 1904, the transit system was supplied 
with power as follows: Power plants at Pratt street, 15,600 
KW; Light dtreet, 2,000 KW; .falls noad, 2,250 KW; Bear Creek, 
675 KW; Black Kiver, 424 KW; uilmore street, 550 KW; and 
Carey otreet, 600 KW, This give, a total capacity of 23,- 
849 KW, The capacities of the substations were as follows: 
Druid Hill, 4,500 KW; nunnery Lane, 1,500 KW; Dugan's 
riharf iPratt street), 2,000 KW, Another plant owned by 
United and located on uharles street was abandoned in 
November, 1903 and leased to the Herald .publishing Company, 
This arrangement could satisfactorily supply necessary power 



-6- 



for the 353 miles of track being operated, but was awkward 
and unsatisfactory rrom an economic point of view. 

flBGINNINaS OF JMOHTEtHM SUBSTATION 

In order to eliminate several of the less effi- 
cient power plants, contracts were let for two additional 
substations. Eastern substation, a 3,000 K.W converter sta- 
tion was completed in September, 1905 at a cost of #94- 
614.64. This station was located on fifteenth otreet and 
Eastern Avenue and began operating on February #7, 1906. 

On June, 1905, the united railways and .electric 
oompany accepted a bid from «J. nenry Miller to construct 
the building for a fifth substation, to be located on j±ar- 
ford rioad. The cost of the building was ^19, 764.84 and it 
was completed early in 1905. This building was of red brick 
construction and was designed to house four rotary con- 
verter units, xhe basement wis constructed so that the passages 
served as air ducts for conducting the cooling air from blower 
to transformers. A balcony was provided for mounting the 
high-voltage oil switches and cables leading to them in order 
to keep this dangerously high voltage equipment away from em- 
ployees. Ducts were built In the front wall for the emergence 
of cables to the trolley structure. 

The necessity for northern Substation, as the 
Harford Road plant is called, was expressed in the general 



-7- 



manager*s report for the year 1904: 

"To strengthen the lines in the northern section 
of our system, a fifth substation will be constructed 
in the vicinity of north Avenue and Harford Road." 
The exact Bite obtained was on Jiarford Road at Holy Cross 
Lane, a short distance north of North Avenue* 

The contract for the electrical equipment for 
the substation was taken by the General Klectric Company 
with a price of $3*B„447..0P,. i'our rotary converters were 
installed in the plant, iiach machine is rated at 1,000 KW 
and operates at a speed of 375 revolutions per minute. 
The machine is wound to operate on 25 cycle alternating current 
at 430 volts and utilizes six phase power. The direct current 
side of the armature is rated at 575 volts. Each rotary has 
three air-cooled 375 KW General Kleotrio transformers; these 
transformers step the voltage down from 13,200 as received 
from the alternating current feeders to 430 volts for the 
armature of the converter; each trans former is tapped at the 
third points so that lower voltages for starting purposes are 
available. 3ince the rotaries of this model are unable to 
start themselves, each has a three-phase, 430 volt, 100 horse- 
power motor mounted on the armature shaft for starting pur- 
poses. 

The high voltage cables feeding Northern substation 



-8- 



from the Pratt Street generating station were installed in 
the city subway as far as North Avenue, and a twenty-four 
duct subway was constructed from riorth Avenue to the sub- 
station at a cost of #4, GOO, The cable for this run is a 
three-conductor, oil-filled type purchased from J. A. 
Roebling for a price of $25,885. 

The high -volt age cable runs through ducts to the 
oil switches, which, as stated before, are mounted in a 
special balcony. The switches are made by the Ureneral 
Electric Company and are rated at 300 amperes and 15,000 
volts, since this power is three-phase, 13,200 volts and 
the converters are six-phase, 430 volts, a diametrical 
connection, with transformer primaries connected in delta, 
is used to impose the alternating current upon the converter 

armature. Diagram one illustrates this connection. 

-I 

Tor cooling the transformers, air is delivered 
through basement ducts at a pressure of one ounce per square 
inch. This air is circulated by a Buffalo i'orge Company 
twenty-five inch blower with a circulating capacity of 20,- 
000 cubic feet per second; this blower is operated by a 
u-eneral electric three-phase, twenty-five cycle, 350 volt, 
7.5 horsepower motor which operates at 500 revolutions per 
minute. The blower is illustrated in figure 3, 

The station 01 is equipped with a complete switch- 
ing apparatus, with indicating and measuring instruments. 




i'lg. 3. 

A View of Rear of Station 
Showing Blower in Background. 
The Oil switches are Visible 
in the Foreground. 




Jf'ig. 4, 

notary Converter No, 1, 
Capacity— 1,000 KW. 
Installed July 7,1906. 




*'ig. 5. 

Northern Substation Today; Ho. 1 House on Right. 




Jfig. z. 

A View of Rear of Station 
Showing Blower in background. 
The Oil owitches are Visible 
in the Foreground. 




*'ig. 4. 

notary Converter No. 1. 
Capacity— 1,000 KW. 
Installed July 7,1906. 




i'ig. 5. 
Northern Substation Today; Ho. 1 House on Right. 



-10- 



Th e Instrument board consists of two sections — an alternating 
current section containing relay switches for the oil s*itches 
and metering devices, and a direct current section containing 
switches for placing various sections of the line on the 
bus bars of the station and meters for measuring the current 
and power being drawn, .figures 6 f 7, and 8 illustrate the 
panel board of the station* 

The relays for operating the oil switches are 
operated by a sixty eel}., lbO volt battery which floats 
across the bus bars through suitable resistors. These 
cells are of the oi-xide type, 

NUMBER TWO HOUoE 

■This first unit of northern substation was over- 
loaded from the time it began operation and an addition be- 
came essential. The report of the general manager in 1907 
said: 

"As the original installation of Northern substation 
was inadequate to carry the load of the sections 
supplied by it, it was considered advisable to con- 
struct an addition to this station, to be known as 
Northern number Two, and the lot adjoining Number 
One station was acquired for this purpose. " 
This additional building was completed in November 1907 and 
equipped with two 1500 KW rotary converters and necessary 

transformers and auxiliary apparatus. An additional three- 



-11- 




Fig 



Alternating Current Panel, 

showing instruments and 

relay switches for oil switches, 




I'ig. 7. 



Direct Current Panel, 
showing instruments and 
switches for various lines. 
Circuit breakers can he 
seen above ammeters. 




.big. 3 
IJewer section of Direct uurrent Panel. 



-12- 



conductor high tension cable was installed from Pratt street 
to this station for the purpose of talcing care of the addi- 
tional load on this substation. The combined capacity of 
these stations was 7000 &W and they were operated from a 
single panel by a single group of operators. The station 
was now capable of adequately supplying power to the entire 
northeastern section of the system, including the outlying 
sections of lork uoad, Towson, and uelair. 

The new building was a three-walled affair built 
upon the north wall of the original building. The architec- 
ture of both houses is identical, number Two house was 
constructed without a balcony for the oil switches to allow 
the mounting of a iiiars twenty-ton crane, a machine omitted 
in the original building and sorely needed. The oil switches 
in the new house were mounted on the main floor.. 

The two rotary converters originally installed in 
the new building were identical, being G-eneral Electric machines 
of 1500 KW capacity, The alternating current side of the arma- 
ture is designed for twenty-five cycle current at 430 volts, 
while the direct current side is rated at 600 volts. The speed 
of the machine is 250 revolutions per minute. Transformers 
of similar make and rated at 550 KVA f with a voltage ratio 
of 13,200 to 430 were installed for the converters. These 
transformers are also air-cooled and tapped at the third 
points for starting purposes. The converters are self -starting. 



-13- 




tfig, 9. 

Converter No. 6. 
Capacity— 1500 KW. 
Installed October IS, 1907 




The oil switches of No. 2 House. 
300 amperes, 15000 volts. 



-14- 



CEKFTBALIZATION OF POWER STATIONS 

After the construction of northern substation, 
and the transfer of two additional units to Pratt street 
generating plant from aoaxiaoned plants, it became possible 
to close down the outlying plants at ^ear Creek, Preston 
Street, Carey Street, ^>ilmore Street, Light Street, Fails 
Road, and Owings Mills, each of which was generating current 

of 

at a cost greatly in excess tec that at Pratt Street. 

The report of the general manager for 19U7 states: 
"The rehabilitation of the uompany's power plants 
and distributing system has made it possible to 
shut down the following direct current, steam 
driven power stations: G-ilmore street, Carey 
Street, tiear Creek, ^ack River, and Preston Street. 
From these plants the necessary equipment for the 
Bay Shore power house was obtained." 
Bay Shore power house was constructed in 1907 to 
supply light and power to uay Shore Park since it was more 
economical to build this station, using equipment from aban- 
doned plants, than to run feeders from Eastern substation. 
This was a 1175 Of plant, meager in comparison to the 25,000 
KW capacity of Pratt Street at this time. This was the last 
power plant built by united. 

In 1908, the .balls Hoad plant was damaged by fire. 
It was deemed advisable to close down and abandon the Jlant 



-15- 



as soon as cables could be run to northern substation. Thus 
in 1909, the capacity of the Pratt otreet plant was £9,400 KW 
and the only other station in operation was the bay Shore 
power plant, used only for service during the season when the 
park was open. The Owings Milla station was kept in operating 
condition but unused. 

Thus #ithin a period of ten years, the power supply 
system of the united nailways and electric Company had changed 
from a wasteful system of numerous generating plants to a 
centralized power system, it then cauld be supplied with ad- 
ditional hydro-electric power from the iwcCall Ferry plant of 
the Pennsylvania vmter and Power Company by running high ten- 
sion cables of the power company to the Pratt street plant. 
The first contract for additional power was signed in 1911 
when 12,000 KW were to be supplied, in that year, the united 
purchased 45,174,700 kWH from the Power company, and generated 
63,003,722 KWH at their fratt street plant. This amount 
being supplied by the Power company was gradually increased 
until the Pratt Street station was operated for emergency 
service at power failures of the Pennsylvania water and Power 
Company. In 1921, Consolidated u-as and JLlectrie Company, 
an anillate of the Power company, purchased the Pratt street 
plant and United bought all of its power from that company. 
Thus United left the generation of electricity to a company 
specializing in electric power supply. 



-16- 



LATER CHANGES AT NORTHERN 0UB0TATION 

In 1911, an 125 £W booster, motor driven, formerly 
used at the Falls woad power plant was placed in regular ser- 
vice at Northern to boost the voltage on the line supplying 
the Yowson section. This line is twelve miles long and the 
booster is adjusted to boost the voltage one quarter volt 
per ampere of load current. This booster set contains a 
m'estinghouse lfcS &W, 265 volt, 470 ampere series generator 
driven by a <<estinghouse 500 volt direct current, 250 amperes, 
5b0 revolution per minute motor. (Fig. 11. ) 

In order to increase the capacity of northern 
substation in 1912 to take care of extra demand expected on 
account of the Democratic national uonvention held that year 
in the city, an adaitional 2000 KW rotary converter was in- 
stalled in that substation «iune 15, 1912. This Was a Jesting- 
house machine, converting twenty-five cycle alternating current 
at 43U volts to £75 volt direct current. The rotary operated 
at a speed of 375 revolutions per minute. Three 750 KVA trans- 
formers of the same make were used with the "lachine and the 
diametrical method of imposing three phase current on a six 
phase machine was utilized. 

In 1913, city ordinances demanded the removal of 
caoles from overhead structures and the switchboard at Northern 
was rearranged to permit the direct current cables to leave the 
building through underground ducts. The work was completed by 



-17- 



October 2, 1914. 

By 1917, the track mileage had increased to 
414.87 miles. In order to operate the new lines of rails 
and to be able to supply the additional load on the system 
due to increased business activity in plants manufacturing 
war materials, it became necessary to further increase the 
capacity of Northern substation, a 3000 KW rotary converter 
with three transformers was purchased from the .vestinghouse 
Electric and Manufacturing Company for a price of #36,500. 
Shipment was delayed due to war conditions and the machine 
was not installed until 1918. operation be&an November 30, 
1918. 

The ratings of this machine, the largest installed 
at -orthern, called for twenty-five cycle alternating current 
at 430 volts. The rotary operated at 250 revolutions per 
minute and the direct current side of armature is rated at 
600 volts and 500 amperes. The three transformers used with 
this converter are each rated at 1125 aVA and are of the air- 
cooled type, xhe high-voltage switchgear for use with this 
machine was purchased from the u-eneral nilectric oompany at 
a cost of |IL0,7QQ. .figures 13 and 14 show two views of this 
rotary converter. 

In 1921, a plan was worked out for improving 
voltage conditions on the outlying xowson and oarney sections 
by using dumber i^'our converter at an eighty volt increase at 



-18- 





Jj'igo 12. 

series Booster of number 1 
House. Capacity — 125 KW. 



Fig. IK. 

number 8 Rotary Converter. 
2,000 KW, 600 Volts d. c. 
.iestinghouse manufacture. 



-19- 



peak hours, The necessary additional bus structure was In- 
stalled. This method of maintaining two bus-bar voltages 
proved satisfactory and it was decided to make the arrange- 
ment permanent. Additional bus structures were installed 
and Converters ivumbenp one, two and Three were adjusted to 
deliver 610 volts to the high-voltage bus. The other ma- 
chines maintained the voltage on the original busses at the 
normal value or 585 volts. Proper switching arrangements 
made it possible to switch the tows on, ij-orsuch .avenue, 
and lork woad lines to either set of busies as desired, 
ihe booster could also be inserted In the Towson and i'ork 
Road lines to further boost that voltage if need arose. 

No important changes were made in liorthern oub- 
station until the rapid development of residential areas 
served by the rielair Road, Harford woad, and Carney lines 
overloaded the power facilities there in 1928. Plans were 
started in that year' for an additional substation in the 
load eenter of that area. The site finally selected was 
on rt'hite and Carter Avenues, Hamilton, Much spare capacity 
was available in existing substations so it was decided to 
use equipment already on hand in the new substation. 

Since the new substation was in a residential 
section of the city, it was decided to build it in a type 
of architecture fitting for the surroundings. In order 
to economize on additional operators, it was planned to make 



-20- 



Hamilton substation, the name given to the new plant, semi- 
automatic, capable of being operated by one man working only 
part lime. The estimated cost was #135,000. 

The new substation was completed in 1929. It 
was supplied with power by two high-tension, three-conductor 
cables from .northern substation, and the two rotaries in- 
stalled there were transferred from existing plants. One 
of the machines, a 2QOG KW. Westinghouse machine, was moved 
from Northern substation where it had been serving as num- 
ber Seven converter, rhe other converter for Hamilton was 
a 1125 KW machine removed from central substation. 

The switchgear formerly used with the converter 
while in operation at Northern was now utilised on the 
high-tension cables feeding the Hamilton station. 1'hus 
it became possible to take the new station out of operation 
by merely opening the oil switches at northern. However, 
this station can not be placed into service from remote con- 
trol from the servicing station and requires an operator 
for that purpose; for this reason it is considered a sem- 
automatie station. The operator is present during the 
peak hours of the morning and leaves the machines in opera- 
tion, knowing the operators at northern will cut them out 
as the load drop makes their operation unnecessary. 

Some trouble developed at northern in the failure 
of operators to realize when circuit breakers on the various 



-21- 



line s had opened until power had been off for a period of 
time. Consequently, a system of signals, whereby a horn 
sounds in the plant whenever any circuit breaker opens^was 
installed. 

RETROSPECT 

From the above discussion, it is obvious that 
rthern substation now has a rotary converter capacity of 
10,000 KW and an additional capacity from booster sets of 
£25 KW. It is served by four high-tension cables which 
deliver alternating current at 13,200 volts from the Pratt 
Street switching house of the consolidated Lras and Electric 
Company. This company generates this current as hydro-electric 
power in its stations at ^estport and Holtwood. northern 
supplies power for the trolleys serving northeastern Bal- 
timore; the exact lines served can be seen on Diagram 2 
which shows a schematic diagram of the entire plant, in- 
cluding both houses, it also relays the high voltage 
power supply to a semi-automatic substation in Hamilton 
and possesses the necessary oil switches ior taking this 
substation out of service, Diagram is shows the exact loca- 
tion of both North earn and Hamilton substations as well as 
the general section of the city served. 

The Baltimore iransit Company now owns and operates 



-22- 




i'ig. 14 

Rotary Converter No. 8 
Westinghou.se Manufacture 
Capacity— 3, 000 KW. 




Fig. 15 



A view of the rear of the 
direct current panel, showing 
610 volt busses and feeder to 
York Road. 







. 




o ° o © "o o 

u o u u 



Diagram 2. 

A schematic diagram of the layout of northern dubs tat ion showing 

connections of machines, feeders, and distribution lines. 

Note especially the two direct current busses, 585 and 610 volts. 



-24- 



^76 miles of street car track. The electrical energy con- 
sumed in 1937 totaled 128,271,436 iOVH, all of which was 
purchased from the Consolidated Oas, Electric Light and 
Power Company. This energy in the form of alternating cur- 
rent at 13,200 volts was transformed into direct current 
within the thirteen substations owned and operated by the 
Transit company. 

CONCLUSION 

As the street car being operated in Baltimore 
grew from the rambling mechanism which maefif its initial run 
on the streets of Baltimore in 1885 to the Presidents' 
Conference Committee car of 1937, the equipment and method 
of power supply developed also. The uneconomical production 
of current in many small power stations gave way to the 
central power plant system. This in turn gave way to the 
use of hydro-electric power, purchased from the Consolidated 
Gas, Llectric Light and j^ower uompany, thus eliminating the 
capital involved in electrical production from the invest- 
ment of the Baltimore Transit uompany. The present organiza- 
tion whereby current is purchased at 13,200 volts, alternating 
current, and transformed into 600 volts direct current in 
efficient converter stations has given the residents of Bal- 
timore dependable, economical transit service of both trolley 
cars and coaches. 



-25- 



BIBLIOGkAPHY 



Mr. A. P. 1'rey, Electrical engineer, Baltimore Transit Go. 

Mr. w. J. Guff , Superintendent of substations and Con- 
struction, saltimore Transit Go. 

Information and oervice department, Baltimore Transit Go. 

Executive Files, Baltimore transit Go. 

The Development of .teierican Street nailways , Charles DeMoss 
Emmons 

street Ka ilw ay_s of Baltimore , united Railways and electric Co. 

Files, Baltimore Sun 

Files, Baltimore i^ews-Post 

S, R, i>eizear, Chief iviaintainer of automatic substations, 

Baltimore Transit Co. 

Sir. Joe tieber, Operator, ualtimore- rransit Go. 
Mr. J. t. i.ane, operator, Baltimore transit Go.