April 7, 1910] 



NATURE 



175 



mate velocity of 15 feet per second. The only conduit 

 at present in service has a sectional area of 254 square 

 feet, and is capable of supplying sufficient water for the 

 operation of six generators at full load. The second and 

 third conduits have not as yet been installed. Just 

 beneath the top of the cliff, behind the power-house, is a 

 long underground chamber 274 feet long, 10 feet high, and 

 16 feet wide, with an arched concrete roof to support the 

 conduit above. Rivetted to the bottom of the main con- 

 duit are seven large tapered steel castings leading to the 

 9-foot valves and penstocks below, each supplying water 

 at 10 feet per second to a single horizontal shaft turbine 

 in the power-house below. 



Spillway and Weir. — The spillway at the end of the 

 conduit, which is intended to prevent water-hammer in 

 the case of sudden loss of load, is little more than the 

 enlarged end of the main conduit, raised and fitted with an 

 enclosed weir and underground discharge. The weir is 

 adjustable as to height, and the discharge tunnel, after 

 a steep initial pitch in the taper from the weir, follows a 

 uniform grade and symmetrical curve while circling about 

 to reach the river in a helix, thus preserving a water 

 column which is smooth and unbroken, of highest velocity 

 and least expenditure of energy. This has the effect of 

 preventing erosion, restricted f!ow, and excessive air- 

 suction, the latter on account of the danger of ice forming 

 from the spray under forced circulation of air. 



Location of Power-house. — The power-house is situated 

 on the river bank nearly at water-level and close under the 

 Horseshoe Fall, and it is an interesting and important 

 point that the full head of water between the upper and 

 lower rivers has been acquired so far as was possible from 

 an economic standpoint, while the huge and costly excava- 

 tions rendered necessary in the previous schemes have also 

 been dispensed with, resulting in a greatly reduced capital 

 expenditure. 



Owing to limited space, the generating station is only 

 76 feet wide, but when completed it will be nearly 1000 

 feet long ; the generating units stand side by side in a 

 single row right down the centre of the building, the tur- 

 bines being on the land side and nearest their source of 

 supply. The space between them and the rear wall is 

 occupied by a gallery, upon which are mounted the oil- 

 pressure governors, each almost over the end bearing of 

 the turbine it controls. 



The mean water-level at the generating station is 

 343 feet above tide, though it varies from 338 to 365 feet. 

 The walls of the generating station are of concrete, the 

 rear wall being 12 feet thick at the bottom and the river 

 wall 9 feet. 



Generating Units. — Each generating unit consists of a 

 horizontal double turbine direct coupled to a generator. 

 The completion of the station and its equipment will be 

 but an extension of the present form until, according to 

 present plans, there will be an installation under the one 

 roof, capable of continuously delivering 200,000 horse- 

 power of electrical energy. Three of the generators, which 

 are all of the conventional horizontal shaft pattern and 

 pxactly alike in appearance, have a capacity of 10,000 

 horse-power each, while the others have each a capacity 

 f 12,000 horse-power. These machines are wound for 

 ■e-phase current at 12,000 volts and 25 C3'cles, and have 



. Giving fields, the revolutions being 187-5 P^f iriinute. 

 i he total weight of each generator is 231 tons, and each 

 was entirely assembled on the spot, including the building 

 up of the laminated iron rotor and the winding and in- 

 sulating of the armature. 



Turbines. — The turbines were made by J. M. Voith, 

 Heidenheim, a. d. Brenz, Germany, and are of the 

 Francis or inward-flow tj-pe, double, central discharge or 

 balanced twin turbines, and are designed to deliver 12,000 

 horse-power at 175 feet head. Their shafts are 24 inches 



iximum diameter, and each carries two 78-inch cast- 



1 runners of " normal " reaction. The housings are 



reinforced steel plates 16 feet in diameter, spiral in 



elevation, and rectangular in plan. Gates are of the wicket 



or paddle type, and the rotating guides forming them are 



carried by shafts which project through stuffing-boxes to 



an external controlling mechanism worked by the 



srovernors, thus freeing the casings from the objectionable 



internal-gate rigging, and leaving the approaches to the 



XO. 21 10, VOL. 83] 



guides uniform and open. Whilst the velocities in 

 housings and draft-tubes are high, corresponding losses are 

 avoided by easy changes of velocity and direction, and 

 large curves free from acute angles or obstructing projec- 

 tions. 



Leads. — The leads from the generators are single con- 

 ductors, insulated with treated cambric. These leads, each 

 in a separate compartment, are mounted on porcelain 

 insulators, ample clearance to earth being allowed every- 

 where ; the compartments are built up of thin shelves of 

 reinforced concrete fastened to the concrete substructure 

 of the power-house, and are closed by asbestos doors readily 

 removable for inspection. At no place are the leads of 

 more than three generators brought near one another, and 

 the leads of each set of three generators, where they 

 approach their respective oil-switches on the gallery, are 

 so protected and isolated from each other that earths or 

 short circuits are impossible. Field circuits, exciter leads, 

 and control wires are carried in iron conduits, and are 

 either in separate passages or at a proper distance from 

 the main wires. 



Distributing Stations. — The generating and distributing 

 stations are parallel, and nearly 600 feet apart, with a 

 difference of 260 feet in elevation. The distributing station 

 is wider and shorter than the power station, and is divided 

 into three longitudinal bays or five main sections. The 

 narrow front bay contains the switches, bus-bars, &c., at 

 generator pressure ; the wider rear bay contains those at 

 transmission pressure. Between these bays is the main 

 middle bay, divided transversely bj' a three-floor switch- 

 board section into two long transformer-rooms. The pro- 

 jecting central bay is utilised as offices. The transformers 

 stand along the centre of the two rooms in groups of 

 three, corresponding in position and capacity to their re- 

 spective generators. Similar apparatus is arranged in rows 

 parallel with each other and with the generating units. 

 Unit values corresponding to the generators in capacity and 

 position are maintained throughout. Thus each generating 

 unit has its individual cables, switches, and switchboard, 

 section of bus-bars, transformers, interrupters, and high- 

 pressure switches complete to the transmission lines, 

 enabling independent operation as an independent power 

 plant, or, through the selector switches, and duplicate 

 sectional bus-bars, the operation of all units in any com- 

 bination of groups, as readily and perfectly as their opera- 

 tion in parallel. 



Transformers. — ^The low-pressure bay contains on the 

 main floor the 12,000-volt automatic oil circuit breakers 

 in double column, and in the chamber beneath only the 

 sectional duplicate bus-bars and their immediate connec- 

 tions. In the transformer-rooms the transformers stand in 

 pits 6 feet below floor-level, and parallel with them, 

 adjacent to the high-pressure bay, are corresponding pits 

 for choke-coils or other protective apparatus. Beneath, 

 and between the foundations, are laid the various systems 

 of piping for water, oil, and drainage, and the main cable- 

 ways to the transformer above. Each transformer is fitted 

 with a recording thermometer, and is of the oil-insulated, 

 water-cooled type, three to a unit, connected in delta on 

 the low voltage, and in star with centre grounded on the 

 high-voltage side. The secondary' potential of each trans- 

 former is 36,000 volts, and, as connected, the resultant line 

 voltage is approximately 62,000 volts. Each transformer 

 has a normal capacity of 3000 k.v.a., and weighs, com- 

 plete with oil and case, approximately 50 tons. They are 

 cylindrical in form, and the three constituting a unit are 

 arranged in a triangular group in the pit. 



Recording Instruments. — The graphic recording instru- 

 ments are of a new type, and comprise voltmeters, 

 ammeters, wattmeters, and frequency and power-factor 

 indicators. They are so connected in the low-voltage 

 circuits that there is a continuous record of each generator 

 as well as of the demands of any set of feeders. In the 

 control-room, the chief operator's position is in the centre, 

 where at his desk he may observe, by means of his instru- 

 ments, every electrical occurrence, and direct his assistants 

 as required. He has his own private telephone system 

 running to all the rooms in the building, and also has 

 direct connection with telephones along the transmission 

 wires. The telautograph is invariably used for communi- 

 cating with the generating station, because of its un- 



