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ELECTRIC RAILWAY JOURNAL · Vol. 67, No. 4 · January 23, 1926 · pp. 152-156.
Power Distribution in the Interborough
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| [Left] Circuit Breakers in Boxes on Columns, with Boxes Open at 156th Street and Alexander Avenue. [Center] Circuit Breakers in Boxes on Columns with Boxes Closed at 129th Street and Lexington Avenue. [Right] Front View of Group of Circuit Breakers in Chamber at 79th Street and Lexington Avenue. |
The Contact Rail Sections Are Interlocked and Connected by Electro-Pneumatic Circuit Breakers and All Are Under Control from a Centralized Station. In Consequence, the Circuit Breakers Controlling an Entire Substation Section Can Be Opened Through an Emergency Alarm Whose Boxes Are Distributed Along the Walls of the Subway.
Articles in this paper last year discussed the numerous safety features and other improvements applied to the rolling stock of the Interborough Rapid Transit Company and other phases of its New York subway rapid transit service. Equal care has been used in the installation of the electrical distribution system to protect against accidents and electrical disturbances, as well as to safeguard passengers against possible delay through interruption.
Primarily the safety features of the system depend upon the sectionalizing of the third rail, the sections being electrically connected by electro-pneumatic circuit breakers, which are under remote control from a centralized control station. In consequence, the circuit breaker controlling a section, besides automatically opening in case of a super-current flow, will open if an emergency alarm is sent from one of the alarm boxes mounted on the subway wall in that section. Reference to this emergency alarm system in connection with the sectionalized distribution system has been made in previous articles in this series, particularly in that in the issue of July 25. In this article an account will be given of the method by which the contact rails are sectionalized and connected up and supplied with energy from the substations, as well as how the emergency alarm works.
The contact rail in the tunnels is protected from the adjacent structures, and particularly from the steel columns, by means of a specially prepared board carried over the top of the rail and supported by properly insulated posts. The cables which furnish power from the substations to the contact rails are of the concentric type that is to say, there is an inner core that is positive, then a layer of insulation, then a layer of wires forming the negative conductor, then more insulation, and then an outer covering of lead. The purpose of this type of cable construction is to localize any trouble caused by short circuits.
At its outer end this cable terminates at a manhole in the side wall of the tunnel where the positive and negative portions of the cable are separated, the negative lead being connected to a bus and the positive lead carried to a circuit breaker. The circuit breaker is of 3,000-amp. capacity and is equipped with an electro-pneumatic valve for the closing operation and a trip coil for the tripping operation. The circuit breaker is mounted on an extra heavy panel. In some cases, these circuit breakers are housed in fireproof boxes and mounted on the columns, as shown in the left hand drawing on page 153, but wherever possible, a separate concrete and steel chamber is constructed as part of the subway structure, as shown in the right hand drawing on page 153.
The negative bus is mounted in a separate chamber immediately adjacent to the circuit breakers. The negative cables are then run from this negative bus to the track rails in fiber conduit, with a sufficient thickness of concrete around the conduit to prevent water from entering it and to protect it from damage that might be caused by its coming in contact with any heavy object, as well as to afford protection against fire.
The positive connection from the circuit breaker to the contact rail is made by means of 2,000,000-circ.mil cable, insulated by an extra heavy thickness of Kerite insulation, and where it is necessary to install this cable on the steel beams it is further insulated by porcelain insulators. This 2,000,000-circ.mil cable is terminated in a specially devised pothead, constructed of concrete where it is changed to four smaller cables more easily to permit of its being bonded into the contact rails to its full capacity. This change in the size of cables is made by a mechanical connector that permits of ready disconnection whenever necessary.
At all locations where it is possible the positive cables are run underneath the track bed in the way already described for the negative cables, except that as a further insurance against the collection of moisture in the conduits under the track the conduit is filled solidly with a cable compound. Some idea of this detail may be gained from a study of the drawing above, which shows one of the several methods of making the connection, the one used depending upon conditions.
Power is furnished to the contact rails from substations located approximately 2 miles apart. The contact rails within the section supplied by power from a substation is in full control of the operator of that particular substation, and he is under the direction of a system operator located in the main power station. This arrangement has been made possible by the control system in use by which each track section receives power through separate feeders and circuit breakers, and it permits the localizing of any trouble to the track section on which the trouble occurs. The contact rails are further sectionalized for reasons of operating facility during times of emergency, particularly at places where crossovers are located and where it may be necessary to turn or divert trains from one track to another around sections where trouble exists. This is accomplished by creating a gap in the contact rail, around which gap cables are inserted for continuity of power, the cables being in series with a circuit breaker.
In the design of this system, one of the fundamentals observed was the elimination wherever posible of any material of an inflammable or combustible character that would tend to create smoke or fumes. Where this was not possible extraordinary preventive measures were followed for the protection of materials of a combustible or inflammable character.
The contact-rail sections fed from each substation are terminated at points midway between adjacent substations by gaps in the contact rail, around which are cables connected to a group of circuit breakers in sufficient number to provide separate and distinct circuit breakers for each track and for each substation. That is to say, at the dividing point between substations each substation has its own set of circuit breakers. These circuit breakers are all bus-connected so that the load in all rails will be equalized. Therefore, each contact rail section generally consists of a section of tunnel in sole control of a substation operator and furnished with power from this substation, with each track and section independently operated and controlled by dovetailing into the adjacent substation feeding section, as shown in the diagram on page 154.
Each section of contact rail between the gaps is designated by a series of letters and numbers for the purpose of ready identification. So far as is possible, the designating letters employed are related to the location of the limits of the section.
The wiring system for the control of the circuit breakers is shown in the large drawing on page 152. Its operation is as follows: In times of emergency, the emergency alarm boxes located throughout the tunnels are operated by any employee at or near the trouble. Operation of this emergency alarm causes the main feeder breakers in the substation to open and simultaneously to open the equalizing circuit breakers at each end of the substation feeding section. The result of this operation is that the supply of power is then discontinued within the limits of the line fed by the substation. Properly authorized officials in the field are then placed in communication with the system operator, when the proper procedure is decided upon for the resumption of operation. On receipt of these instructions the system operator issues the necessary orders to the substation affected.
This system of control wiring involves the use of control cable throughout the entire length of the subway. This cable is carried on the walls of the tunnel, so that in event of electrical disturbance in cables in the duct line it will be as far removed from trouble of this sort as possible. It is of a rubber-covered type, with specially designed outer covering and support, and of necessity is made up of many conductors, the number of conductors depending upon the number of circuit breakers to be controlled by a particular substation.
The description of the contact rail system just given applies only to the tunnel portions of the Interborough Rapid Transit Company. While the general features of the contact-rail system on the elevated structure of the company are somewhat similar they differ in a number of particulars, especially on the outlying sections of the elevated structure.
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| Typical Wiring Diagram of Remotely Controlled Circuit Breakers Controlled from a Substation (No. 23). |
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| At Left, Pillar Support and Housing; for Circuit Breaker In Subway. At Right, Pit Location for Circuit Breakers with Typical Cable Run. |
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| Detail of One Method of Making Contact Rail Connection. | Cable Connections at 82nd Street Lower Level, Lexington Avenue Line. |
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| Portion of Positive D.C. Feeder Layout Showing Location of Substations, etc. |
Sources: Electric Railway Journal, McGraw Hill Company, Digitized by Microsoft, Americana Collection, archive.org.
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http://www.nycsubway.org/articles/erj-1926-irt_power_distribution.html
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