Power plant for Toronto & Niagara Power Company

THE POWER PLANT OF THE ELECTRICAL DEVELOPMENT COMPANY, OF ONTARIO.

BY F. O. BLACKWELL.

The power plant of the Electrical Development Company was designed to utilize 11,200 cubic feet per second of water under a head of 135.5 feet. The water is diverted from the Niagara river at Tempest Point, midway between the headworks of the Ontario Power Company and the Canadian Niagara Falls Power Company.

The general plan of development adopted called for the construction of a wing wall to gather the water from the rapids, the excavation of a forebay of sufficient capacity with the river at its lowest future stage, a wheel pit, and a tailrace tunnel discharging under the centre of the Horse- shoe falls, where the flow of water over the falls is greatest.

The forebay in the rapids and the tunnel outlet under the falls were both bold and original conceptions, which were thought at the time to be practically impossible of execution.

In order to uncover the forebay it was necessary to construct a coffer dam 2,200 feet long in the rapids, where for a portion of the way the cribs had to be sunk in water twenty-six feet deep and running at a velocity of twenty-two feet a second. This work was started in April, 1903, and proved to be an extremely difficult under- taking, but was successfully completed in about twelve months.

The tailrace tunnel was started in May. 1903, by the sinking of a construction shaft on the bank of the river 150 feet deep and fifteen by seven feet inside the timbering. From this shaft a drift fourteen feet wide and seven feet high was run 670 feet to the portal of the tailrace tunnel, work upon which was only actually started in December of the same year. The final opening under the falls proved very difficult on account of the large amount of water encountered near the face and the mass of detritus that had to be cleared away by men exposed to the full force of the wind and spray from the falls.

The wing dam is 785 feet long, and its maximum height is twenty-seven feet. The elevation of the crest is 527 feet, and there will be from three to eight feet of water flowing over it, depending upon the condition of the river. Near the power-house the dam is cut away for a length of thirty feet to an elevation of 524 feet so that there will be three feet additional depth of water to carry away ice from the submerged arches in front of the power-house. This question of guarding against ice is one of the most important problems which had to be met. In addition to the first line of submerged arches just referred to, a second wall has been constructed outside of the racks. The spaces between the outer and inner walls, and between the latter and the racks, are arranged each with a spillway at one end, so that such ice as passes through will float out at the north end of the building.

The wheel pit is 416 feet long and twenty-two feet in width inside of the brick lining, which is two feet thick, and is spanned by masonry arches at three levels to carry the machinery. The ends of the pit are also closed by arched wall linings. The arches were not allowed to he put in until the pit had closed in as much as it would and come to rest. There has been no movement whatever at the union of the arches and the walls that the most accurate observations could detect, which is interesting on account of the theory once advanced that there was a periodic change in the distance apart of the sides of the pit.

For the power to be developed the length of the wheel pit is much less than in previous developments of this character. This is due to the penstocks alternately being on the right and left-hand sides of the water-wheels, permitting one hoistway to serve two wheels.

The water after passing through the racks enters a cast-iron bell-mouth, which in turn joins on to a riveted steel pen- stock ten feet six inches in diameter.

There are eleven penstocks, and at the head of each there is an electrically operated gate to control the water. The pen- stocks are connected at the bottom to water- wheels of 13,000 horse-power capacity, running at a speed of 250 revolutions per minute. The wheels and penstocks rest on a heavy concrete foundation, which covers the bottom of the wheel pit.

The hydraulic apparatus is being furnished by the I. P. Morris Company, of Philadelphia.

Each wheel unit consists of two Francis internal discharge turbines five feet four inches in diameter. The discharge of water is to be governed by cylinder gates, and the weight of the moving parts will be partially taken by a water piston in the wheel. There is a single cast-iron draft tube nine feet in diameter for each wheel, and the units alternately discharge water underneath the east and west tail- race tunnels. The object of the under discharge is to seal the draft tubes and prevent loss of vacuum, no matter what July 28, 1906

the elevation of the water in the tunnels may be, and without the necessity for a tailrace weir. By using two tunnels it is possible to shut off the water entirely from one-half of the wheels without interfering with the other half. By closing down the wheels, discharging water into either tunnel, that tunnel will drain itself, and there is no necessity for closing off the mouth of the tunnel. A gate is provided at the mouth of both tunnels, however, in case of extreme back-water, which has been known to be fifty feet above normal in the lower river.

As the wheel pit is not connected to the tailrace, the hydraulic apparatus can never be flooded out.

The tunnels on each side of the wheel pit are twenty-five feet deep, and vary in width from sixty-six to thirty feet, with a velocity of from fifteen to twenty-one feet a second. Ata point about 150 feet north of the wheel pit the tunnels come together. At the junction the tunnel is thirty-five feet wide and twenty-five feet six inches high and tapers to a width of twenty-three feet five inches and a height of twenty-seven feet one inch, which section is carried to the edge of the falls, a distance of 1,935 feet. The slope of the main tunnel is .005, making the total loss about ten feet, and the velocity is twenty-six feet a second. The tunnels have a lining two feet thick throughout of concrete faced with brick, except for 300 feet at the north end, where the lining consists of concrete rings in six-foot sections, which are expected to break off as the falls gradually wear away. This is necessary, as the crest in the centre has been receding at an average rate of two and one-half feet a year.

The power of the water-wheels is de- livered to the electric generators through vertical shafts 150 feet long, consisting of riveted steel tubes thirty inches in diameter between bearings and _ solid shafts fourteen and one-half inches in diameter at bearings. This shaft is held at three points in the wheel pit by steady bearings resting on concrete arches. At the upper end there is an oil thrust-bearing thirty-seven and one-half inches in diameter fed by oil under a pressure of 350 pounds, which is sufficient to carry the weight of the entire revolving parts should the water thrust fail from any cause,

There will be ultimately eleven 8,000- kilowatt generator units, four of which are now being installed by the Canadian General Electric Company. These are of the revolving field type and run at a speed of 250 revolutions per minute. They deliver three-phase alternating current at a periodicity of twenty-five cycles and a potential of 12,000 volts. There are at first to be two 500-kilowatt water-wheel driven exciters in a room underground, and two motor-generator sets of the same capacity on the generator floor. Eventually three sets of each type will be installed. any two of which will excite all the alternators.

The controlling switchboard for the entire plant, including transformers and transmission lines, is located in the centre of the power-house, where the operator can see the generators. It consists of an enclosed compartment with a bench-board in front and doors at the ends. The instruments which are ordinarily employed in the operation of the station face toward the generator room. On the back are the recording instruments and switches, which are only occasionally used or referred to. Dummy bus-bars and signal lamps on the bench-board clearly indicate to the operator the connections in the station, and the instruments are so located that they are over the switch which controls them. The generator instruments, for instance, are over the generator control switch. The board is so compact that an operator standing in front of it can see all the instruments from one position, and can conveniently reach all the controlling switches. The power-house bus-bars, generator oil switches, instrument and switch transformers are located immediately below the power-house floor in brick compartments. The wiring arrangement is such that a generator can either be connected to the bus-bar or to a separate outgoing cable. In ordinary operation the current from each generator will leave the building by the shortest possible route, and there will be practically no cables running the length of the power-house.

The power-house will be a handsome building in the style of the Italian Renaissance, about 500 feet long and seventy feet, wide. The height will be forty feet, except at the centre and end bays. The centre bay will stand out from the face of the building, and, besides being the main entrance, will give room for the offices of the power company. On the inside it will afford space for the switchboard and auxiliary apparatus. The power and transformer houses are 1,817 feet apart, and will eventually be connected by four underground conduits. One conduit will be in reserve, and the plant will not be crippled unless two conduits should simultaneously fail.

At present two conduits only are constructed, each with sixteen four and one-quarter-inch ducts placed two wide and eight deep. The manholes are common to the two conduits, but are divided into two parts by a central partition, so that one duct system would not be damaged by a burnout on the other.

The cables required for the portion of the power plant first installed are six 500,000 circular mils triplex for 12,000-volt power, two 00 B. & S. for the switch motor bus-bars, two with forty-five Nw. 8 B. & S. wires for oil-switch control, two each of thirteen No. 12 and fourteen No. 7 wires for instrument connections. The cables are in duplicate, and either half of the ducts might be disabled without shut- ting down the power system.

The transformer house is on top of the bluff outside of the park limits, and is de- signed to accommodate fifteen 2,670-kilowatt transformers furnished by the Canadian General Electric Company, twelve of which are now being installed. These transformers are of the oil-immersed, water-cooled type, and are wound for 10,000, 11,000 and 12,000 volts primary and 60,000, 50,000 and 40,000 volts secondary. They will be connected in delta on both primary and secondary sides.

Each transformer is placed in a separate closed fireproof room, so as to minimize the fire risk and prevent the possibility of trouble in one transformer being communicated to others. The transformers are mounted on rails and arranged to slide out of the compartments into a gang- way, where they can be readily handled by an overhead traveling crane.

The piping for oil and water is placed in the basement under the back of the building and on the wall of the trans- former compartments.

The cables from the power-house are carried in ducts to a gallery above the transformers, where the 12,000-volt switches, instrument transformers and bus- bars are located.

The high-potential bus-bars, wiring instrument transformers and air switches for the 60,000-volt circuits are located in the room back of the transformers, and connected through the gallery floor to the high-potential oil switches on the floor above.

The outgoing transmission lines leave the building through porcelain bushings at the back, and are protected by lightning arresters on the wall below.

The wiring throughout is completely enclosed in brick compartments, the only openings being through asbestos doors placed at points convenient for inspection.

The transmission line to Toronto, constructed by the Toronto & Niagara Power Company, is built on a private right of way eighty feet wide, which can later be used for a double-track railway. With this idea in view, the line was located so that the maximum grade at no point need exceed one per cent, and the minimum radius of track curvature can be made as low as a quarter of a mile.

Two complete steel tower transmission lines will eventually be constructed, one only being erected at present. Each tower carries two circuits of 190,000 circular mils copper conductor. The standard distance between poles is 400 feet, although much longer spans are used in crossing rivers and ravines. For curves and long spans special extra heavy towers are employed. with double and triple insulators. The height of the standard tower is sufficient to support the lower cable at a height of forty feet from the ground. Fifty and sixty-foot towers are made by bolting ex- tensions to the bottom of the standard towers, and are used wherever there are depressions along the right of way. In two places towers 150 feet and 175 feet high are required in order to cross navigable channels at the Welland canal and at Burlington Beach.

The copper cable consists of six strands with a hemp centre, and has a tensile strength of 60,000 pounds, and = an elastic limit of 40,000 pounds per square inch. It was made by the Dominion Wire and Cable Company, of Montreal.

A large portion of the power is delivered to synchronous apparatus, the Toronto street railway employing rotary converters, and the lighting company synchronous motor-generator sets. The loss of power, when transmitting 10,000 horse-power to Toronto over each circuit, will be less than sixteen per cent, and either line can transmit 20,000 horse-power with less than twenty per cent loss should the other become disabled.

The insulators are fourteen inches in diameter and fourteen inches high, and are tested for a potential of 120,000 volts complete, or 60,000 volts on each of the three parts of which it is composed.

The transmission towers are heavily galvanized after all machine work upon the parts has been completed. They were made by the Canada Foundry Company, of Toronto, and the Riter-Conley Manufacturing Company, of Pittsburg, Pa. At points exposed to severe lightning the line will be protected by twelve-foot extensions carrying galvanized steel cable above the power conductors.

There will be three division houses along the line, dividing it into four sections, any one of which can be cut out for inspection or repair. The length of the line is about ninety miles, and the di- vision houses will therefore be twenty-two and one-half miles apart. A lineman will control each section daily after the transmission is in operation.

The substation in Toronto is designed for fifteen 2,670-kilowatt transformers, and is similar to the transformer house at Niagara falls, except that there will be double low-tension bus-bars and a much larger number of feeder cables for distributing power throughout the city of Toronto.

The switchboard is located at one end for controlling the transmission lines, transformers and 12,000-volt circuits. This is equipped with dummy bus-bars with all necessary instruments.

In the plans of the Electrical Development Company every effort has been made to avoid any interruptions to the power service. No single accident or any probable combination of accidents is ever likely to shut down the entire plant. The double ice protection, twin tailrace tunnels, the extra 8,000-kilowatt water-wheel, generator and transformer unit, and the du- plication of the transmission lines and of all auxiliary apparatus is with this end in view.

The engineering design of the plant is in charge of Dr. F. S. Pearson as consulting engineer. The water power development was planned by H. L. Cooper, chief hydraulic engineer, and the writer laid out the electric plant. The construction of the hydraulic work and power-house was originally under Beverly R. Value, and is now in charge of L. J. Hirt as resident engineer, and Walter Pearson as electrical engineer.

The transformer houses and transmission line were built by Robt. C. Brown, chief electrical engineer of the Toronto & Niagara Power Company.

The officers of the company are: president, H. M. Pellatt; first vice-president. Frederic Nicholls; second vice-president, William Mackenzie; manager, H. H. Macrae; secretary, H. G. Nicholls; treasurer, D. H. McDougall.