Publication: Sacramento Daily Union
Sacramento, CA, United States
Technical Description of the Sacramento System.
Interest Awakened in It Among the Business Men of the World.
The following technical description of the works of the Sacramento Electric Power and Light Company, which appeared last week in the New York "Engineering News," will be read with interest in connection with the report in yesterday's "Record-Union" of the excursion of business men to Folsom on Wednesday:
The completion of the power transmission scheme between Folsom and Sacramento, Cal., is the conclusion of a vast enterprise, undertaken in doubt and terminated in a success which has demonstrated not only the tremendous resources of power in the State of California, but also the commercial feasibility of electrical transmission over long distances. A sketch of the progress of the work, including a view of the dam at Folsom. was given in our issue of April 11, 1895. In what follows we give an account of the electric plant in somewhat greater detail.
The hydraulic apparatus, manufactured by S. Morgan Smith of York, Pa., consists of four pairs of 30-inch wheels of the McCormick horizontal shaft turbine type, each pair of 1,266 HP. capacity at 300 revolutions operating under a head of 55 ft. The steel penstocks are 8 ft. in diameter, and each wheel has two draft tubes. The governors are of the Faeseh-Picard type, and these are assisted by heavy fly wheels fitted to the water wheel shafts. The hydraulic plant also includes two special horizontal wheels for the exciters.
The power house is a two-story brick building. The water wheels are placed in the open air between the forebay and the wall of the structure, through which the turbine shafts pass. To each shaft is coupled a 750-K-W. (1,000-HP.) Genera] Electric three-phase generator, the largest of their type yet constructed. Each is a 24-pole machine delivering current at 60 cycles, 800 volts and running at 300 revs, per min. The exciters are 4-pole, 500-volt, 30 K-W. generators, either one of which is of sufficient capacity to excite the fields of all four generators. From the generators the current passes to the generator switchboard, and thence to nine step-up transformers, each of 250-K-W. capacity in the upper story of the power house. The transformers are cooled by an air blast from blowers driven by induction motors. In these transformers the pressure is raised from 800 to 11000 volts, and from them the current passes to the high-tension transmission line.
The switchboards are of Tennessee marble, and are so arranged that the generators may be run in parallel or on separate lines, as may be desired. The generator switchboard carries the necessary switches, instruments and other apparatus for synchronising the generators. The boards in the transformer room carry switches for the high and low tension sides of the transformers and switches and current indicators for the transmission lines.
The pole line is double throughout, and follows the highway from Folsom to Sacramento, a distance of twenty-four miles. Each pole carries two crossarms for two circuits, each circuit contesting of three bare copper wires supported on double petticoated porcelain insulators, especially designed and made for this installation at the porcelain factory of the General Electric Company at Schenectady. Each insulator before shipment was exposed to a test of not less than 25,000 volts alternating. Each circuit can carry the output of one dynamo, and any dynamo can be thrown on any line. The line loss is calculated at 7.5 per cent, when transmitting 3,000 H. P.
The telephone line is carried on the same poles as the transmission line, and connects the power house with the sun-station in Sacramento. The transmission lines being spiraled every mile, and the telephone wire transposed every fifth pole, no induction is noticeable on the telephone circuits, and conversation is not in any way interfered with.
The sub-station is a fireproof two-story brick building on the corner of Sixth and H streets, Sacramento, having the transformers on the second floor and the dynamo-room on the ground floor. In the transformer-room the high-tension switchboards receive the terminals of the 10,000-volt lines and operate the different combinations of the step-down transformers. These transformers, twenty-one in number, fifteen of 125 K-W, and six of 40 K-W capacity, vary in size, according to the duty required of them, the secondaries delivering current at 125, 500 and 1,000 volts. They are also ventilated by blowers.
The transformers are connected to high and low-tension switches on the boards, and from these the current passes to the distributing hoards for the synchronous motors, power circuits and incandescent lighting.
In the main or dynamo-room of the pub-station a line shaft runs the entire length. To this are directly coupled through friction clutches, three synchronous motors, each of 250 K-W capacity, wound for a potential of 500 volts and run at a speed of 450 revolutions. To the line shaft are belted one 200 K-W. and one 90 K-W. multipolar G. E. railway generators and two 100 K-W, Edison bipolar machines, all of 500 volts, and three 100-light and two 75-light Brush arc machines. In this room are also the switchboards for controlling the synchronous motors, the railway generators and circuits and the arc dynamos.
For the operation of the synchronous motors 750 K-W. of transformer capacity is utilized, the balance being used for low and high-tension distribution. The low-tension current is distributed by a three-phase, four-wire system, combining the three-phase and Edison three-wire system —i. e., three wires for the three-phase current and a fourth or neutral wire. Incandescent lights are connected between the neutral and any one of the three other wires, while motors are connected to the three-phase wires, giving at the mains 115 volts for lamps and 200 volts for motors. The feeders for this extensive system pass from the sub-station through a distributing switchboard, which carries potential regulators for maintaining constant pressure at the mains. Additional circuits run from the sub-station at 500 and 1,000 volts, supplying current for lights and motors in the more distant parts of the city.
Power was transmitted for the first time from Folsom to Sacramento on July 14. 1895, for the operation of the Sacramento Street Railway. On September9th a grand carnival was held to celebrate what up to the present is the longest commercial power transmission ever effected. The balance of the machinery has since been set up, and the installation is now complete.
The power transmitted is now being used for manufacturing purposes as well as for lighting the city and running the street railway. The power is much cheaper than generated by steam, and it is interesting to note that the steam engine is fast disappearing from Sacramento factories. Among the establishments now using the power are Hour mills, box factories, machine shops and hotels.
The largest consumer is the street railway, which has over twenty-four and one-half miles of single and seventeen miles of double track, and operates thirty-two motor cars and trailers. The Southern Pacific Railway shops employ a large number of motors for drawbridges and in freight sheds. The Buffalo Brewing Company is about to install five nonsynchronous motors to replace steam engines which have been in use years, and expect to save 40 per cent, of the present cost of operation by the change.
The entire equipment was carried out by the General Electric Company, whose apparatus is exclusively employed. This plant is a complete illustration of the possibilities of electric transmission, every problem to be met with in transmitting power over long distances at high potentials and utilizing it having been solved successfully. The best indication of this success is reflected in the value of the interest paying obligations, the bonds of the Sacramento Electric Light and Power Company finding ready purchasers at par, although the plant has been in operation less than one year.