Fig. 32.—Foundation of Power-station at Spier Falls.

Fig. 33.—Plan of Power-station at Great Falls.

[Larger plan] (207 kB)

At Electra station on the Mokelumne River five pairs of impulse wheels are direct-connected to five generators, each unit having its shaft diagonal with the walls of the building, and pipes deliver water to the wheels under a head of 1,450 feet. The ground plan of the generator room at this plant is 40 by 208 feet. The power-station on Santa Ana River, whence energy is transmitted 83 miles to Los Angeles, measures 127 feet long and 36 feet wide inside, and contains four generating units in line, each of which consists of a direct-connected dynamo and impulse wheel, with shafts parallel to the longer sides of the station. Jets driving the wheels in this station are delivered under a head of 728 feet minus the loss by friction in a penstock 2,210 feet long.

Fig. 34.—Power-house at Red Bridge on Chicopee River.

Both of the first Niagara plants, with vertical wheels far below the stations in the pits, are long and narrow and have their generators in a single row. The later of these two stations has a ground area of approximately 72 by 496 feet outside, and contains eleven generators all in line. From these examples it may be seen that the prevailing type of electric water-power station, whether designed for horizontal or vertical wheels of either the pressure or impulse type, is wide enough for only a single row of generators and wheels, and has sufficient length to accommodate the required number of units.

A few modern stations that depart from this general plan will be found, as that at Great Falls, on the Presumpscot River, whence electrical supply for Portland, Me., is drawn. This station sets about forty feet in front of the forebay end of the dam, and two penstocks enter the rear wall, while the other two enter one each through two of the remaining opposite sides. Of the four generators, with their direct-connected wheels, two are arranged with parallel shafts, while the other two have their shafts in line and at right angles to the lines of the former two. The station containing these generating sets has a floor area of 55 by 67.5 feet.