Sacramento line uses special GE porcelain insulators


Publication: The Sacramento Daily Union

Sacramento, CA, United States
vol. 91, no. 85, p. 3, col. 1-2


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 1,260 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.) General 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 11,000 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 consisting 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 sub-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