Power Transmission at Duluth, MN Used Fred Locke Insulators

Power Transmission at Duluth, Minnesota. F. W. Springer.

(Electrical World and Engineer, vol. XXXV., April 14, 1900, pp. 545-547.)

The St. Louis River drains an area of 38,000 square miles, composed of pine land, swamps, lakes, and some arable land. The rainfall is about 30 inches per annum, and there are two periods of low water, one from summer drought, and the other from the freezing-up of the small streams and swamps, many of which freeze solid. The minimum flow occurs in winter, when the power may be estimated at 15,000 HP. at a head of 600 feet. Recently a St. Louis power development company has been formed, and it is proposed to cut a canal 4 miles in length and to lay 800 feet of pipe line to a power station in the bed of the stream. This will give 350 feet head, or about 10,000 HP. at minimum flow.

The Black River scheme is similar to the above. A masonry dam 20 feet high is to be built, which will give a head of 55 feet and a flow of water of 6,000,000 cubic feet. The pipe line is to be 54 inches diameter, and will be buried to prevent freezing. Two direct-connected polyphase 800-kilowatt generators are to be installed, together with five (one reserve) oil transformers for raising the pressure from 440 to 18,000 volts. The pole line will consist of 35-feet cedar poles, 8 inches diameter at the top and set 52 to the mile, with three pin cross-arms and 24-inch spacing. The conductors will be No. 1 bare copper mounted on three part Locke insulators.

The interesting point about these schemes is that, although many propositions have been made and much money spent, the development of the power running to waste did not become practicable until the application of long-distance transmission by electricity. With the prospect of the immediate development of such powers it looks as though what had long been hoped for would come to pass—that is, the beginning of the manufacture of iron and steel at Duluth and Superior. It is estimated that it will not cost more than $55 per HP. to distribute the power.