For instance, on a 150-mile line in California transmitting 745 kilowatts (10,000 horse power) at 40,000 volts, aluminum conductors seven eighths inch in diameter are used. In a 100-mile, 60,000-volt transmission line in Mexico a copper wire three-eighths inch in diameter is used. The transmission line from Shawanigan Falls to Montreal, Canada, employs aluminum con ductors carrying 12,000 horse power at 50,000 volts. Steel-cored aluminum conductors are also used for this purpose and in some of the latest high tension transmission lines steel-cored copper conductors are utilized.
To provide a system that will be as nearly absolutely reliable as practicable duplicate cir cuits are in the majority of cases constructed, in order that if one circuit becomes inoperative the other may immediately be brought into service. In some cases the two circuits are erected on one set of poles. In others two separate pole lines are built.
Wherever possible private rights of way are obtained for the transmission line and it is of advantage to have this way so wide that danger from falling trees shall be avoided. Rights of way along steam railway tracks are not con sidered desirable for the reason that the smoke from the engines very soon so impairs the insulating quality of the insulators that frequent cleaning and washing of the insulators is rendered necessary. Even on private routes the cleaning of the insulators is at times essential to maintain the insulation.
The distance to which electric energy can be profitably transmitted from a source of elec tric power is not yet definitely determined. Much depends on the cost of fuel at the dis-; tributing points and the amount of energy to be delivered. In California, where coal is dear,
electric energy is now being commercially trans mitted from a number of water-power plants in that State to an amount exceeding 100,000 horse power at a pressure of 40,000 to 60,000 volts and to distances ranging from 50 to 230 miles. In Switzerland electric energy from water power is transmitted to the point of consumption and sold at $20 per horse-power hour per annum. There the price of coal is $6 to $8 per ton, but labor is cheap. Electric energy gen erated •by the force of falling water and trans mitted 85 miles by wire is sold in Montreal, Canada, at $15 per horse power per annum at a profit. But while as stated the distance to which electric energy may be commercially transmitted is yet undetermined, calculations have been made by reputable electrical engineers which indicate that under proper conditions electric power may ultimately be profitably transmitted in large quantities, say 200,000 kilo watts, and at a pressure of 170,000 volts, to a distance of 500 miles. This transmission would entail the employment of copper wires of a diameter so large that the dissipation of energy by brush discharges between the conductors would be avoided. Should this conception be realized it would obviously bring New York, Chicago and other large cities within reach of the electrical energy developed at Niagara Falls. Indeed the calculation just referred to was based upon the amount of mechanical power utilized in New York. Consult