Energy Distribution on the New York, Westchester, and Boston Railway (1912)
Electric Railway Journal · Vol. XXXIX, No. 24, June 15, 1912
Compound Catenary Construction on a Four-Track Curve.
A Description of the Overhead Line Construction on the Latest Single-Phase Electrification - Writing and Supporting Structures of the Latest Approved Design - One Section is Equipped with a New Type of Catenary.
The New York, Westchester & Boston Railway, as described in the Electric Railway Journal for May 25 and June 8 is unique in being the only strictly suburban electric railway in the country which has not been built up from an older road as a basis. The project consisted in building a high-speed road for 21 miles through practically virgin territory which when given adequate transportation facilities was certain to provide a heavy traffic. In consequence, the builders were unhampered by the necessity of following any definite collection of standards and were in position to select for use only the best features which exist in the practice of the present day.
It was, of course, axiomatic that electricity should be used as a motive power. However, the determination of the most desirable system of electric traction was a problem of considerable magnitude into which so many variable factors entered that its solution was impossible except in its application to the individual case. The use of direct current furnished through substations is universal with the transportation systems of New York City, and several of these will eventually make practically physical connection with the new railway. On the other hand, however, a very substantial precedent for the use of single-phase alternating current existed in the successful installation of that system on the New York, New Haven & Hartford Railroad. When all the relevant factors were considered, the alternating current system appeared to be more desirable. and this decision enabled the new railway to take advantage of the extended experience of the New York, New Haven & Hartford Railroad with that system. In fact, the latter company has carried out the electrification of the new railway and has been represented by P. J. Kearny, the engineer in charge of electric traction, in the design and installation of the power circuits of the new railway. The benefit of this experience has been shown by the fact that, notwithstanding the brand-new condition of the entire line, not a single delay or accident has occurred since power was turned on. In general the overhead construction is quite similar to that now being installed on the Harlem branch of the New York, New Haven & Hartford Railroad. However, on the New Rochelle branch of the new line a trial installation differing from the standard form of construction has been installed.
Since the road is constructed through practically unsettled territory, the requirements for some years to come will be very much less than the estimated ultimate schedule, The latter is expected to be approximately six and one-half times the initial schedule, or 11,700,000 car miles per annum against a present condition of 1,772,000 car miles. The power requirements were established by means of a load curve based on the operating schedule and which is shown in the cut on page 1051. This gives the hourly loads existing during an average day under winter conditions. As shown by these curves, the maximum demand for current under the ultimate schedule amounts to 17,200 kw, which, however, will not last over a full hour, so that the average hourly demand amounts to 16,600 kw. The average hourly demands, both for the ultimate and the present schedules, are shown by the dotted lines at the peaks of the curves.
At present the equipment consists of thirty cars, of which six are held in reserve so that the average annual mileage of each car is estimated at 61,500 miles. The requirements of the ultimate schedule will be approximately 150 cars. The cars, which were described in the Electric Railway Journal of March 30, 1912, collect current from the overhead wires through a pantograph and step the line voltage of 11,000 volts down to approximately 250 volts at the motors. The weight of each car fully equipped is 119,000 lb. The motors are of the single-phase type and have an hourly rating of 175 hp. Two are installed on each car and are operated by indirect control.
Power is received from the Cos Cob power station of the New York, New Haven & Hartford Railway and is purchased from that company at a flat rate. The connection is made at the end of the New Rochelle branch, where it approaches the main line of the New Haven. This point is 16 miles away from the generating station, and, notwithstanding the fact that the power is delivered through four No. 0000 feeders which are also to be used for the Harlem branch of the New Haven railroad, the calculated transmission loss is only 3 percent. This is a striking example of the advantages of the high-tension single-phase system. In this connection it is planned to convert the present arrangement into a 22,000-volt, three-wire system whenever this contemplated change is made on the main line of the New Haven.
The line voltage is maintained exactly at 11,000 volts by means of a Tirrill regulator at the power station which controls that leg of the three-phase generator supplying the line. The two other legs of the generator cannot be regulated owing to the variable field required on the active leg. These windings are, however, used to supply three-phase current for operating elevator motors, pumping water and similar purposes, and an additional wire to complete this auxiliary three-phase supply is carried along the line.
Feeders And Bonds
At New Rochelle four No. 0000 branches are taken from the main line feeders of the New York, New Haven & Hartford Railroad and carried along the tracks on the catenary bridges to Columbus Avenue. At this junction point two of the No. 0000 feeders are carried south along the four-track section of the railway to the New York end and two others are carried north along the two-track branch to White Plains. Circuit breakers are located between these feeders and the overhead lines at New Rochelle and Columbus Avenue and also at intermediate points approximately in the centers of both the four-track section and the White Plains branch. These circuit breakers do not operate on ordinary overloads, as the experience of the New Haven road has established the fact that it is undesirable to have them do so. There is extended along the line a control wire which is connected with the overload relays at the power house switch house. Unless this control wire is energized by these relays none of the line circuit breakers can open. The overload relays at the power house switch house automatically throw resistance into the circuit prior to opening, so that the current involved by a short circuit is greatly reduced and, on this account, a short circuit on the line, owing to the control wire, does not cause the opening of any of the line circuit breakers except the two immediately affected by the fault.
Line circuit breakers are in every case located on overhead anchor bridges. The feeders are also divided into sections by circuit breakers, the sections being cross connected at the ends by a bus wire which extends across each anchor bridge. Westinghouse switches and transformers are used throughout on the line.
The rails are bonded at the joints with duplex bonds concealed by the angle bars and composed of stranded copper having a cross-section equivalent to No. 0000 wire. The bonds are of the steel pin terminal type and are 24 in. long. Cross bonding is provided every 3000 ft. at the center of the impedance bonds which are at the ends of the track signal circuits. No return feeder is used, the track being ample to carry the small return currents.
Lightning protection for the overhead lines is afforded by means of the grounded main messenger cables or main supporting strands which carry the track conductors of the compound catenary construction. Protection for the single catenary construction on the New Rochelle branch is provided by a grounded wire carried above the feeder wires on the catenary bridges. This wire is shown in the illustrations of the single catenary construction as supported by a pin at the extreme top of the posts. The apparently limited amount of lightning protection is due to the fact that the insulators on the line have an extremely high safety factor, 110,000 volts being their electrical strength. This is ten times the working voltage, but experience on the New Haven railroad has shown that the increased safety which the excess insulation provides is quite inexpensive and reduces insulator trouble absolutely to accidental breakage through exterior causes.
Compound Catenary Construction
Compound Catenary on Double-Track Tangent.
The four-track section of the line extending from Harlem River to Columbus Avenue is all equipped with a compound Catenary. At shown in the accompanying page illustrations, this consists of a main supporting cable of 7/8-in. extra-high-strength steel strand carried over the top member of the catenary bridges and fastened to them with cast-iron clamps. These wires are in consequence grounded. Between each pair of bridges are two intermediate cross bents composed of 3-in. I-beams weighing 5 1/4-lb. per foot and clamped to each one of the main supporting cables. Hung from the intermediate cross bents are track catenary supporting strands of 5/8-in. extra-high-strength stranded steel cable. These cables are insulated from the intermediate cross bents by 110,000-volt insulators, which were furnished by the Ohio Brass Company. Underneath the track catenary supporting strands and hung from them at 10-ft. intervals by means of standard New Haven type hangers is a horizontal No. 0000 grooved copper wire, and 2 1/4-in. below this is a No. 0000 grooved steel contact wire. These two wires are connected at 10-ft. intervals by clips spaced so as to come midway between the hangers from the track catenary supporting strands. The alternate spacing of clips and hangers gives a high degree of flexibility to the contact wire. At curves, however, the hangers are attached directly to the clips. This is done to preserve the vertical alignment of the two wires independent of side strains. Flexibility is obtained through the angularity of the hangers which exists on all curves. The illustration of the single catenary at the end of a tangent shows this feature, which is the same in both types of catenary, the change from alternate spacing of clips and hangers to coincident location of the two taking place directly under the catenary bridge shown in the foreground.
Compound Catenary on Double-Track Curve.
The hangers are composed of a 1/4-in. steel rod threaded on the end and screwed into a hook-shaped casting which hangs over the track catenary supporting strand. The rod is screwed into the casting until it rests solidly against the supporting wire and holds the hanger securely in place. On tangents the lower end of the 1/4-in. hanger rod is screwed into a casting of which the lower part forms a clamp which fits into the groove of the track conductor cable. This clamp is made up of two pieces of malleable iron held firmly in the groove of the cable by means of a 1/4-in. flat-head machine screw which passes through both pieces of the clamp. On curves, where the hangers are fastened directly to the clips which hold the track conductor and the contact wire together, the lower part of the hanger is bent to the proper angle, so that the track conductor can take its proper position over the center of the track, and the end of the hanger passes horizontally through the clip. This horizontal end of the hanger is upset to form a shoulder and the end is threaded for a 1/4-in. nut. The threaded end is passed through a hole in the clip and the nut on it is set up until the clip grips the two wires on account of the pressure between the nut and the shoulder. The clips between the track conductor and the contact wire are standard throughout the entire line. The upper portion of the clip is extended to surround the upper wire completely, but the lower portion does not extend below the groove in the contact wire.
At turnouts where two contact wires have to be brought together a special clip is used which consists of three parts, one of which it placed between the two wires, the other two parts forming the outsides of the clamp. All three parts are gripped firmly on the two wires by means of 1/4-in. machine screws passing through all three parts. These clips are approximately 6 in. long and have two screws to each clip in order to exert more gripping pressure than is provided by the ordinary clip. This is required on account of unbalanced tension in the diverging wire. The clips and hangers are exactly similar to those described in the Electric Railway Journal for April i6, 1910, page 700. Their use is standard on the New York, New Haven & Hartford Railroad, where they have been in successful use for several years. The spacing of 10 ft. both between the hangers and between clips is maintained over the entire line.
Bridges are spaced 300 ft. apart on all tangents. At curves, however, and at some of the overhead highway crossings the spacing has to be reduced. On curves up to 2 deg. the track conductor and contact wires are centered on the track by offsetting the points of support of the main supporting strands on top of the bridge. This condition is shown in the foreground of the illustration of the four-track curve. Curves of over 2 deg. have the catenary bridge spacing reduced in accordance with the curvature to a minimum of 200 ft. On curves of over 4 deg. deflection, pull-off poles ore erected between the bridges and the main supporting strand receives a side strain by means of 1/4-in. steel strand pull-off wires. A great deal of care has been used in centering the contact wires over the truck. The results are shown in the various illustrations of curves. In general, the construction has permitted a practically perfect alignment with the track curve so that at no time is the contact wire out of line with the center of the pantographs on the cars.
Cable Supports Under Low Bridge.
On curves or at other points where the bridges are brought closer together than the standard spacing of 100 yards the shorter span involves a decreased deflection of the main supporting cable in order to avoid unbalanced strain on the bridges. At such points bracket hangers, composed of two pieces of angle iron set 45 deg. from the vertical are introduced between the main supporting strand and the intermediate cross bent in order to make up the space between them, as the contact wire is maintained at a constant elevation of 22 ft. above the rail except at low overhead bridges. For such special cases the minimum height is approximately 17 ft. Typical bracket hangers are shown in the illustration of the four-track curve. At anchor bridges an especially ingenious method of isolating adjoining sections of the line without causing an actual break in the circuit has been devised This is shown in the accompanying line cut of the arrangement. It will be seen from the cut that there is exposed to the pantograph a continuous surface of live contact wire, but that the contact wires on each of the two adjoining sections at the anchor bridge are isolated from each other by insulators and by an air gap of 18 in. The objection to introducing a break in the contact wire is, of course, the damage which is done by the heavy arcs which are drawn off in breaking a circuit on account of the high voltage impressed on the line. At overhead bridges or stations the wires are supported on insulators hung from an I-beam which in turn is clipped to the bottom of the bridge member by a short piece of angle iron. The construction is shown in the half-tone on page 1011. This represents simple catenary construction. In the compound type the main messenger strand is clipped to the bottom of the bridge; leaving the rest of the construction exactly the same as for the single catenary. The main messenger strand is, as before mentioned, grounded so that no insulator is needed between it and the bridge.
Pantograph Deflector at Turn-Out.
At turnouts or crossovers where necessity exists for two contact wires to be brought together a deflector has been devised to prevent a pantograph from being caught on the diverging wire. As shown in the illustration on page 1007, this deflector is made up of small steel T-bars inverted and bent up at the ends to provide a horizontal guide between the two diverging contact wires. The pantographs on the cars are 5 ft. in transverse length and the deflector begins at the point where the two contact wires are 5 ft. apart, extending in toward the point of the "'V" formed by the two wires until the space is reduced to 2 ft. The cross members shown are supports for the guide and are fastened on top of the copper track conductor wire at the clips. The two pieces forming a "Y" at the end of the guide are carried at the same level as the guide, sloping upward so as to ease the blow of a pantograph passing at high speed. The necessity for the deflector at turn-outs is on account of shock with which the side of the contact shoe of a slightly tilted pantograph strikes a diverging contact wire. The deflector rides up gradually on the pantograph and holds the wires clear until the pantograph has gone far enough toward the point of the "V" to permit both wires to ride on its contact shoe. When this condition exists the danger of the wire catching on the side of the shoe or being struck heavily by it is past.
The double-track branch between Columbus Avenue and White Plains is equipped with a compound catenary, and this is exactly similar to the four-track construction in all respects except that of width on bridge.
Single Catenary Construction
Single Catenary at End of Tangent.
The New Rochelle branch has been equipped with the single catenary construction in order that the merits of this arrangement may be thoroughly tried out. Its action should be watched with interest. The difference between the single catenary and the compound consists in the elimination of the main supporting strand and the intermediate cross bents. The catenary, which is composed of 1/4-in. extra-high-strength steel strand, is swung over the clear length between adjoining catenary bridges arid is hung from 110,000-volt insulators fastened to the under side of the trusses. The No. 0000 copper track conductor wire and the No. 0000 grooved steel contact wire are hung from the catenary with hangers and clips in exactly the same manner as in the compound catenary construction. The only difference is that the hangers are, of course, very much longer at the points of support, the true catenary span being 300 ft. instead of the 150 ft. span of the compound type. The bridge spacing for the single catenary is 300 ft. on tangents, reducing to approximately 200 ft. on the sharpest curves. The contact wire over curves has a side strain given to it by pull-off wires either attached directly to the bridges or else to bridles between two adjoining bridges. Pull-off poles are located between bridges on curves greater than 4 deg.
Single Catenary Construction at Curve.
The bridges which carry the overhead wires are of steel construction throughout and are supported on concrete foundations. In general the vertical posts are made up with four corner angles and diagonal lattice work on all four sides made of flat steel bars set at 45 deg. and riveted together at the intersections. At the bottoms of the posts 1/4-in. gusset plates are riveted to the corner angles and the two sides which stand parallel to the track have 6-in. x 6-in. x 1/2-in. angles riveted to them to form lugs for the anchor bolts. The posts for the four-track section measure 2 ft. lengthwise with the track at both the top and the bottom, but the dimensions at right angles with the track are 1 ft. 3/4 in. at the bottom and 2 ft. 2 in. at the top, so that the cross-section of the post, viewed parallel with the track, shows a smaller dimension at the bottom than at the top. The reason for this is that the point of greatest moment occurs at the top of the post where it is joined to the bridge members which cross the track. The same general design applies to double track.
Four-Track Anchor Bridge and Circuit Breakers.
Gusset plates of 5/16-in. steel are riveted to the two sides of each post which stand at right angles to the track. This provides a solid side for the top 3 1/2-ft. of the post. To these gusset plates are riveted the cross bridges, which for the four-track construction are made up of two trusses 3 ft. 6 in. deep. The top and bottom members are made of heavy angles and are connected by diagonals and verticals made up of angles which are fastened to 5/16-in. gusset plates at the points of intersection. The two trusses are tied together with a single lattice work of 2 1/2-in. x 1/2-in. x 5/16-in. angle at the top and at the bottom. Diagonal cross-frame supports between the two trusses are installed every 13 ft. to prevent any tendency to buckle. On tangents the distance between the top of the truss and the top of the rail is 31 ft., but this is reduced under special circumstances. Double-track bridges have trusses 3 ft. deep but are otherwise similar. In all cases the top and bottom truss members are sufficiently heavy to avoid necessity for carrying loads at the panel points.
Four foundation bolts are set in pairs on the two sides of the post which stand parallel to the track. The bolts in each pair are 24 in. apart and all are carried down 7 ft. 2 in. into the concrete foundation, where they terminate with 1/4-in. anchor plates 8 in. x 2 ft. 4 in. in size. The bolts are made of 1 1/4-in. round steel upset and are threaded for a 2 1/4-in. nut at the ends. The foundations for the four-track construction have top dimensions of 3 ft. 6 in. x 3 ft. 6 in. and are spread out by three steps each 2 ft. high to dimensions of 7 ft. x 8 ft. Below this, if necessary, the concrete is carried down to good bearing soil. On curves where the side strain is heavy the foundation dimensions are increased to 8 ft by 11 ft.
The design of the catenary bridges has been varied to suit the different loads which come upon them and no attempt to make universal standard was carried out. The construction of the bridges on curves differs from that on the tangents and the four-track bridges are considerably heavier than the two-track. In general, however, the design of all bridges was based upon a condition wherein all wires were surrounded by a coating of 1/4 in. of ice, or, in other words, the diameter of each wire was increased 1 in. The dead weight of ice and wire was computed on this basis. The wind load was then taken at 6 lb. per square foot of projected area, including the coating of ice, or 20 lb. with bare wire.
This method of establishing the loading is an arbitrary one based upon the fact that during a period of heavy wind the ice coating would be shaken off the wires so that the two conditions of maximum ice load and maximum wind load would not occur together. The condition of a wind load of 6 lb. plus a dead load due to 1/4-in. coating of ice was found to be the most severe on curves owing to the additional pull of the wires on account of the low temperature. On tangents the worst conditions were found to be caused by the wind load only on bare wire.
Overhead Line Maintenance
Emergency Line Car with Working Platform Raised.
Special provision has been made for continuity of electric service. The circuit breakers which separate the road into five different sections are installed at the anchor bridges. The latter are located at the terminals of the four-track section and the two double-track branches. Intermediate bridges are also located at the Columbus Avenue junction and at the middle points of the four-track section and of the long White Plains branch. By means of the circuit breakers any one of the tracks in any of the sections can be cut out of service for making repairs. No live line work is attempted, as the high voltage and grounded overhead wires make such procedure too dangerous. Whenever work is to be done on any one of the lines it is first isolated by the circuit breakers at each end of the section and the line is then grounded to the rail with a temporary connection as a further protection against accidental charging.
Gas-Electric Repair Car
Lowering Emergency Line Car Platform.
One of the most interesting features of the line-maintenance methods is the gas-electric repair car with which the road is equipped. This car has a General Electric gasoline-engine-driven d. c. generating set which supplies current to motors on the axles for running the car, and also to motors for operating the revolving jib crane which is shown in the illustration. The crane, which was built by the Whiting Foundry Equipment Company, has an adjustable hook which is available for all kinds of light wrecking work, the capacity being 10 tons on a lift close to the car, or 3 tons when the hook is at the extreme end of the boom. This hook is also used to elevate the lineman's platform. The latter process is accomplished by catching the hook in a frame which extends down from the platform, the latter rising on four parallel-motion arms, each pivoted to the boom at one end and to the ends of the platform at the other.
This device keeps the platform horizontal at all times. The platform can be raised to any desired height and, as shown in one of the illustrations, the boom can be swung sidewise so that the linemen can work over tracks adjacent to the one on which the car happens to be standing. The car, being independently operated, can go to any point on the line, regardless of whether the current is on the line or not. The maximum speed is about 30 m.p.h.
Lighting and Power Circuits
The main power circuit, including the feeders, receives single-phase current from the power house at 25 cycles. Lighting for the stations is transformed from this circuit through duplicate transformers at each station to 110 volts.
Switches at each station are provided to permit using any one of the feeders for the lighting supply so that the continuity of the lighting circuit is assured. However, in the underground section of the line which runs for 4000 ft. north of Morris Park an emergency service from an exterior source is contemplated. This connection will be strictly an emergency one and is only to be used in case the main supply of power from the Cos Cob power station should fail completely. Power for operating motors, elevators and air compressors as required on the line is transformed from a three-phase, 11,000-volt circuit, of which one leg is composed of the main feeders, another leg composed of the track return and the third leg composed of a power wire which is carried overhead on the catenary bridges.
The overhead circuits therefore comprise the following were, in addition to the track catenaries: on the New Rochelle branch, four No. 3 signal circuits and four No. 0000 feeders, two of each of which are located on each side of the track; on the four-track section, four No. 3 signal wires, two of which are located on each side of the track, one No. 0000 feeder on each side of the track, and one No. 3 third-phase power wire and one No.3 control wire for the circuit breakers on opposite sides of the track. The branch to White Plains has the same wire arrangement as the four-track section. The third-phase wire and the control wire are brought from the point of intersection of the road with the New Haven at Mount Vernon. They are not carried over the New Rochelle branch, as there are no motors or circuit breakers except at the ends of that section.