The Electrification of the Hoosac Tunnel

[Trade Journal]

Publication: Transaction of American Institute of Electrical Engineers

New York, NY, United States
vol. 30, no. 2, p. 1391-1456, col. 1


ELECTRIFICATION ANALYZED, AND ITS PRACTICAL APPLICATION TO TRUNK LINE ROADS, INCLUSIVE OF FREIGHT AND PASSENGER OPERATION

 

BY WILLIAM S. MURRAY

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General Catenary Construction

 

In the simultaneous authorization of the electrification of the six-track Harlem River Branch for freight and passenger operation, the New York Westchester & Boston and the Hoosac Tunnel, it naturally made it imperative for the engineers of the New Haven Road to prepare a very extensive set of plans to cover completely these three constructions. Illustrative of the flexibility and adaptability to standardization of the single-phase system, while the Harlem River six-track work required a longer and stronger bridge than the four track New York Westchester & Boston railroad, the general design of both, however, are the same; and notwithstanding the difference in number of tracks, the wire plans for the overhead catenary system of the four-track were applicable to the six-track, the simple addition of two tracks merely meaning an additional 50 per cent increase of material and an equal percentage of weights and stresses for the bridges to sustain.

Space does not permit a lengthy discussion of the general drawings and plans that have been presented in this paper. Owing to the necessary reduction, in reproducing the tracings, the figures on the illustrations and particularly those of the strain and deflection tables, have been reduced to sizes which are difficult to read, without the aid of a glass. However, in including these drawings, my thought was that they would be an epitome of the extensiveness of the work under way, and give some idea of the methods involved in its general specification.

It will be of interest, no doubt, to state that in all the New Haven electrification drawings, it has been the attempt to make each one, while descriptive of the construction desired, at the same time a specification of procedure in erection.

In the case of the New York Westchester & Boston and the Harlem River electrifications we were able to assign to this work Mr. P. J. Kearny and Mr. L. S. Boggs, respectively, who had had previous catenary construction experience with the New Haven, and who were in touch with the methods pursued in its electrification work.

In the case of the Hoosac Tunnel electrification, coming at the same time as the two previous works referred to, and finding ourselves lacking the necessary engineer for this work, Mr. L. B. Stillwell, of New York, was offered and accepted the position as engineer in charge of this work, reporting to the engineering department of the New Haven road, of which Mr. E. H. McHenry is vice-president. As indicated in the prints included in this paper, covering the Hoosac Tunnel catenary construction, it is to be noted that these all bear a similar appearance to those relating to the two other electrifications previously referred to. While the electrification of the tunnel and its approaches is not yet complete, it is rapidly nearing this stage. Electric locomotive operation for instruction of engineers has already started on the North Adams approach of the tunnel in anticipation of regular service.

The Hoosac Tunnel electrification is characteristic for its simplicity. In the case of its power house, two turbo-generators each of 3000 kw. capacity were installed, with a provision for a third generator of similar capacity. The New Haven company was able to utilize the plans as developed for its recently installed Waterbury station, certain adjustments and additions, however, being required to be made to these plans due to difference of location and size of two of the generating units and switching arrangements necessary to the Hoosac Tunnel single phase conditions. The locomotives have been referred to before; they are characteristic for their simplicity, the cabs being roomy, the control apparatus being centrally arranged and most accessible to inspection.

The power house is located 2.4 miles from the track catenaries, and Fig. 43 shows the general wiring diagram of the complete system. Again space does not permit an extensive description of this electrification. Naturally the most interesting part of it is the tunnel itself. The introduction of 11,000 volts into this tunnel, with the close overhead clearance that the doubletrack arrangement requires, afforded an interesting problem in the location and placing of insulators which would insure against any breakdowns between the electrified wires and ground.

 

FIG. 43. - Hoosac Tunnel general wiring diagram
Fig. 43. - Hoosac Tunnel General Wiring Diagram

 

FIG. 44. - Hoosac Tunnel catenary bracket
Fig. 44. - Hoosac Tunnel Catenary Bracket

 

From the crown of the tunnel is suspended a bracket, as shown in Fig. 44. Four insulators, each capable of resisting 150,000 volts to ground, are installed on this bracket. Two of these insulators apply to each track. Their arrangement of support is such as to place them in series, thus giving them a combined dielectric strength of 300,000 volts. The outside insulator holds the track messenger, to which is pendent the contact wires below. Some criticism might be offered in using a 150,000 volt insulator, where 40,000 might have sufficed. By the expenditure of $1 more per insulator, there was secured practically eight times the insurance from breakdown. The tunnel is five miles long—an unhandy place to come to a full stop. There are 1000 insulators; hence $1000 has been spent to secure eight times the protection.

On the approaches to the tunnel, insulators of the design as shown in Figs. 45 and 46 are used. The opportunity here seemed an excellent one to secure immunity from trouble; 50 cents extra per insulator secured practically three times the protection offered by an ordinary 40,000-volt insulator. The outside insulators before erection are all required to withstand a dry voltage test of 110,000 volts.

 

FIG. 45. - B. & M. Main line insulator
Fig. 45. - B. & M. Main Line Insulator

 

FIG. 46. - Hoosac Tunnel.  Insulator for yard catenary
Fig. 46. - Hoosac Tunnel. Insulator for Yard Catenary

 

It has been forcibly impressed upon the writer that it is good engineering to spend money on insulation. All of the insulators purchased for the Hoosac Tunnel electrification, inclusive of the tunnel itself and its outside approaches, did not total one half of one per cent of the total expenditure. Insulation is of all things the one most important thing to be right, in order to secure continuity of service. It pays a handsome dividend every year. It has been said by our electrical superintendent, Mr. H. Gilliam, that the emergency train service on the New Haven electrified lines would practically cease if line failures were eliminated. This means that mechanically everything is fit. There is no reason why the electrical condition cannot be made identical.

So much with reference to our plans of main line electrification, in which I believe there can be recognized a general sense of inherent standardization, notwithstanding they refer to three properties with a variety of service and location.

In a previous part of the paper the electric switch engine has been referred to.