Niagara Falls 100.000-Hp. Development

Niagara Falls 1 00,000 Hp. Development [ 39 600,000-Hp. Line Delivers Niagara Power Six Circuits Spaced for 88,000 Volts Are Supported on Cantilevers Overhanging Hydraulic Canal—Special Precautions to Guard Against Failure By J. ALLEN JOHNSON Electrical engineer Niagara Falls Power Company | ^HE problem of transmitting the 100,000 hp. generated in the Niagara Falls extension was I complicated by many factors. In the first place the prospective load for this develop- ment was concentrated within a comparatively narrow area adjacent to the upper river, so that it was neces- sary that the entire output should be transmitted in a single direction. The city has few available streets leading in the desired direction, and most of these were already occupied by conduit systems. As a second consideration, the character of the load, which has a daily load factor of over 95 per cent (the power being mostly used for electrochemical and electro- metallurgical purposes), is the worst possible for under- ground transmission because the constant generation of heat in the cables causes a considerable reduction in their transmitting capacity compared with that on a system of low load factor. As a third consideration, a glance into the future indicated the probability of a much larger transmission of Niagara power to Buffalo in the not distant future, requiring a much higher voltage than that used for local distribution. In this event the proper location for the step-up transformers would be close to the generating station. A 3-mile (4.2-km.) underground transmission to Echota, the center of load, at generator voltage before stepping up would be economically unsound. Furthermore it appeared very probable that additional development of power at this point would be required in order to meet the double demand for more power on the one hand and increased economy in use of water on the other. Overhead transmission would permit the necessary high voltage for long-distance transmission and would also provide the necessary flexibility to care for future increases in power development, either by- adding more circuits or by raising the transmission voltage. In addition to all other considerations, cost estimates showed a differential in favor of overhead transmission of about one to three, which under the existing conditions of high costs was an extremely im- portant consideration. Fortunately, the company already possessed in its canal right-of-way through the city a possible outlet for overhead lines if a way could be found to utilize it without interfering with its use as a waterway. As finally constructed the transmission line has a length of 16,000 ft. (4,800 m.) and runs from the terminal building up the canal to the river, thence following the bank past the plant of the old Niagara Falls Power Company (now known as the Niagara plant) and finally turning away from the river again at Echota to connect with the Echota substation. The solution of the transmission problem was greatly facilitated by the consolidation of the two power com- panies inasmuch as land for the location of the line for the greater part of its length was already in possession of one or the other of them. For a distance of approxi- mately 4,000 ft. (1,200 m.) through the heart of the city, however, it was necessary to make use of the property already occupied by the hydraulic canal. The accompanying halftone illustrations show clearly how this was accomplished by means of steel cantilevers anchored into massive concrete foundations on one bank of the canal, upon which were erected the six-circuit transmission towers. For the greater part of the distance it was only found necessary for the narrow bases of the towers to be placed over the canal right-of-way, easement being ob- tained from abutting property owners for the over- hanging portion of the construction. At the large bridge spanning the canal at the junction of Third and Niagara Streets, however, this was not possible, and it was necessary to place two towers entirely over the canal. This was accomplished by means of cantilevers extra heavily braced. The main horizontal members of this structure are composed of two 30-in. (75-cm.) I beams, each 60 ft. (18 m.) long, placed side by side. Thirty feet (9 m.) FIG. 53—ROUTES FOLLOWED BY PRINCIPAL TIE LINES AND FEEDERS OF NIAGARA FALLS SYSTEM of these beams is buried in the massive concrete foun- dation, the other 30 ft. projecting out over the canal. In these structures the center line of the towers is 25 ft. (7.5 m.) from the face of the canal wall. A heavy brace was added to these special structures to give stability and rigidity, although not needed for strength. In the case of the short cantilevers the brace was omitted. In addition to the special narrow-base towers used on the canal section, the local conditions called for the use of several other types of structure. In full-strain posi- tions three different types were employed, the stand- ard-strain type, portal strain, and two-circuit strain. Between strain points the line is supported on flexible steel bents of portal construction. The portal type of construction was used for the section along the river bank where the line is built over a future street. For a distance of approximately 1,000 ft. (300 m.) the land which this street is to occupy has not yet been filled in, and the towers were erected on heavy concrete abutments constructed in the