Niagara line & Imperial insulator

[Trade Journal]

Publication: American Electrician

New York, NY, United States
vol. 8, no. 8, p. 268-270, col. 3,1-3



The Niagara-Buffalo transmission was inaugurated on Nov. 16, one minute after midnight with unqualified success, and electrical power from Niagara is now used to propel the electric cars of a number of important lines in Buffalo, the amount used being 1000 HP.

The transmission line is 26 miles long and passes over a private way. It is carried on shaved cedar poles painted white, ranging in height from 35 to 60 ft., according to the locality, and from 60 to 75 ft. apart. The poles are set 6 to 8 ft. deep, some simply placed in the clayey ground and tamped, while others, in moist, and soft earth, are set in concrete. The pole line was erected by the White-Crosby Company.


Fig. 1 Section of Porcelain Insulator.


Each single pole carries three cross arms, the upper two for the transmission wires, and the lowest for a telephone circuit. The transmission cross arms are of yellow pine, 12 ft. long X 4 3/4 ins. X 5 3/4 ins. Each arm will carry six insulators, three on each side of the pole, but three only are now in place screwed to wooden pins. On the outer end of each upper arm are two 18-in. iron pins on which is strung a galvanized barbed iron wire, which, grounded every fifth pole, serves as a lightning arrester.

The line consists of three conductors of bare copper, of 350,000 cm. cross-section, each conductor being a nineteen-strand cable. Complete transposition of the wires is effected every five miles. These conductors are strung on porcelain insulators of heavy pattern, made by the Imperial Porcelain Works, Trenton, N. J. These insulators, one of which is illustrated in Fig. 1, have the appearance of large inverted soup bowls, with a cap having a longitudinal groove and two wings and a special drip-way on the upper surface. Beneath they have two deep annular grooves, to prevent any moisture connecting the outside of the insulator and the supporting pin and thus cause a ground. Each insulator weighs about 12 lbs., and before acceptance was subjected to a test of 40,000 volts alternating. Failure in the smallest degree insured rejection. The conductors lie in the longitudinal grooves and are tied to the wings.

The total length of the line is 26 miles, and as the three-phased system demands the use of three circuits, the total length of conductor is 78 miles, the cable for each mile weighing about 5200 lbs. With a transmission of 1000 HP at 10,000 volts, the total drop is less than 3 per cent., the line being designed for 5000 HP.

The last 4200 ft. of the line is underground through a subway consisting of twelve ducts of vitrified tile laid in four layers of three each, each duct having a diameter of 3 ins. in the clear. The twelve ducts are surrounded on all sides with 4 ins. of concrete as a protection, and the top of the concrete is 18 ins. below the surface. This conduit is laid along the canal bank, and has sixteen manholes.

The overhead line from Niagara dips to a terminal house and is connected through lightning arresters to the underground cable, which runs along a short tunnel connecting the terminal house with the first manhole of the conduit.

The underground cable was supplied by the Safety Insulated Wire Company, and is insulated with 9/32 in. thickness of rubber, then braided and sheathed with a heavy lead armor. This cable was tested to 40,000 volts for acceptance, and to 30,000 volts for experiment. It is said to have withstood the latter test without revealing weakness in the insulation. The conduit continues as far as the transformer house a small one- roomed brick structure, built in the rear of the Niagara Street power house of the Buffalo City Railway Company.


Fig. 2 Step-Down Transformer Station Buffalo.


The two-phased currents from the great 5000-Hp generators revolving in the power house at Niagara, passes at a voltage of 2200 to the main switchboard. That portion intended for Buffalo is led in lead-covered cables over the bridge across the canal, where the cables are connected to the two-phased low-potential switchboard. From this they descend into an air-tight chamber in which are built the transformer supports.

In this room, large enough for a man to move about in comfortably, all connections between the low-tension two-phased lines and the step-up transformer wires are made, the cables being supported by large porcelain insulators on iron brackets.


Fig. 3 Step-Up Transformer Station Niagara.


The "step-up" transformers now in position (Fig. 3) number two, and are rated at 936 KW each. They represent the latest practice in transformer design, are the largest yet constructed, and of the air blast type. Into the air-tight chamber beneath the transformers air is forced by a 60-in. blower, driven by a 5-HP multipolar direct-current motor. The coils of the transformers are arranged with the major axes in a vertical plane, and two main passages are provided one through the iron of the core, and the other through the spaces between the coils. Through the open cast iron pedestals on which the transformers stand a blast of cool air passes directly into the main air passages and thence into a number of minor air ducts in the transformer. The admission of the air is regulated by dampers, which may be adjusted independently either for the coils or the core.

The step-up transformers are 94 ins. high, and each weighs 25,000 lbs. They raise the voltage from 2200 volts to 11,000 at present, but are designed to allow of a voltage of 22,000 by a change in the connections. They stand on frustrums of rectangular pyramids mounted on an iron framework and are encased in suitable iron frames, the frame being provided on the top with cast lugs by which they may be readily handled with the traveling crane which runs along the roof of the transformer house.

It is in these transformers that the two-phased system is abandoned. From them three currents issue differing in phase by 120 degs. The connections are brought out at the bottom, and continue to the high tension marble switchboard for connection to the transmission lines. The equipment of this board is of special design to permit of the handling of the high voltage current without danger. Each conductor from the transformer is connected to a single-pole switch of quick-break type, mounted on heavy insulating pedestals, and separated from its neighbor by a barrier of marble much higher than the closed switch and about one inch thick. These three switches control the output of any two of the 935-KW step-up transformers which may be connected for either 11,000 or 22,000 volts. Each conductor has its fuse carrier of special type designed for this transmission. Each carrier is twenty-four inches long and is forced into contacts mounted, like the switches, on large insulating pedestals. Each has two handles, and the construction is such that they can be removed from the board for the insertion of new