Publication: Electrical World
New York, NY, United States
The Lachine Rapids-Montreal Electric Power Transmission System.
LACHINE Rapids, in a certain sense, made Montreal. The St. Lawrence, navigable for boo miles from the sea for large vessels, here descends a chain of turbulent rapids, and here Jacques Cartier halted in his attempt at a westward passage to China. Three hundred and sixty-two years later the rapids, which mark the head of navigation and determined the position of Montreal, are harnessed for the service of the city which has grown op below them. The scheme of obtaining power from these rapids is by no means a new one, having been proposed and forgotten a dozen times within the century. It was not until the perfection of electrical transmission methods. however, that work was seriously begun.
In 1895 the Lachine Rapids Hydraulic & Land Company commenced the construction of the great water-power-development works at the rapids, and, after exploiting a project for the direct utilization of the power at the wheels, decided to transform the whole output of their plant into electricity, and transmit it to Montreal, or elsewhere, as might be profitable. The engineering work done under the auspices of this corporation is bold to a degree, being in some respects without precedent, and both its financial and engineering promoters are worthy of the greatest credit for their persistence in the face of many natural obstacles and much adverse criticism.
The Lachine rapids are divided into two channels by an island, the Isle au Heron, and the smaller division, on the left, or Montreal side of the St. Lawrence, was chosen for the scene of the power development. Here, in the current of nearly 15 feet per second a dam, parallel to the shore and about a mile long, was constructed, and the channel thus formed blasted out and deepened. The dam is, for the most part, built of 12x12-inch timbers, filled with boulders. Its facing is of two thicknesses of 3-inch plank, with broken joints, and in general cross section it is square. The crest is sloping and is topped with heavy hemlock logs, squared on three sides, the fourth side, with the natural curvature of the tree, being uppermost. At the upper end of the channel, between the dam and the shore, which is about moo feet wide, a number of heavy piers support a boom to deflect floating ice into the main current of the rapids. The wing dam ends in a granite pier adapted for ice breaking, and built of heavy stones, solidly keyed together by a peculiar construction.
At a point about 1200 feet from the lower end of this artificial canal a cross dam of dressed stone 1000 feet long serves to give the necessary difference in level, and to contain the whole of the hydraulic machinery. Upon this is built the power house, which is probably the largest structure of its kind. This building consists of three dynamo rooms and four rooms for the wheel gearing, the whole being 1000 feet in length, 61 feet wide at the dynamo rooms and 40 feet wide at the other portions. It is solidly built of steel beams, having brick walls in the dynamo portions and a corrugated iron exterior with a lining of heavy felt, and a ceiling of matched hoards in the other parts. The roof is celled inside throughout and slated for its whole length. The floor is of steel I beams and concrete covered with one-inch slate slats in the dynamo rooms, and heavy boarding in the connecting portions.
The seventy-two turbines are of the vertical shaft pattern, each 57 inches in diameter, and giving, at 83 r. p. m., with the normal head of 16 feet, 300 horse-power each. Six of these are attached by bevel gearing to each of the twelve horizontal dynamo shafts. The wheels are of a submerged type, having cylinder gates and no draft tubes. The massive bevel gearing consists of a steel pinion on the dynamo shaft and a crown gear on the wheel shaft, provided with maple teeth, the combination proving very effective and singularly quiet in operation. The most interesting feature of the hydraulic plant, however, is the governing mechanism, one governor controlling each gang of six wheels.
A sensitive ball governor is operated at a high speed by a belt from the main shaft. This controls a scale-beam lever, having at each end an electrical contact and steadied by a small alcohol dash pot. The electrical contacts control two powerful electromagnets adapted to move a pair of friction discs, keyed on the main shaft, to the right or left. These engage with other friction discs, to which are connected a powerful screw gearing which controls, through a system of levers, the cylinder gates of the six wheels. These gates are counter-weighted to decrease the effort necessary for their control. The governor will shut off all the water from full head in nine seconds, and under ordinary running conditions is almost as perfect in its control of the wheels as the best types of steam engine governors. These machines, as well as the wheels and gearing, were made and installed by the Stilwell-Bierce & Smith-Vaile Company, of Dayton, Ohio, to whom much of the credit for the successful performance of the plant belongs.
The dynamos are to be twelve in number, although only four are now in operation. These machines are of the revolving field type, and are rated at 750 kw each. They are wound for three-phase current at 4400 volts direct from the armature, and operate at a periodicity of 60 cycles per second at their normal speed of 175 r. p. m. An exciter is provided for each machine, consisting of a 40-kw four-pole generator, giving 150 volts at 875 r. p. m. These are belted from pulleys on the main shaft, and the four for each group of four dynamos are worked in parallel. These exciters also furnish current for the electrical governors previously mentioned. Both dynamos and exciters were built at Peterborough, Ont., by the Canadian General Electric Company.
The permanent switchboards, of which there will be three, one in each dynamo room, are not yet installed. They will be of a simple type. The temporary switchboard for two dynamos is of white marble and contains three single