There is an increasing demand everywhere for electrical energy at low cost. The cost of
producing, and more particularly of transporting fuel, has increased to such an extent that the generation of electricity at many places where it is to be used makes its supply impossible at commercial rates. This has led to generation at economic points, and its distribution over long distances to its market by means of high tension transmission lines. The term " High Tension " is, of course, an electrical and not a mechanical one in this case. The location of the generating station may be at a point where fuel is cheap, or more generally where water power is available either by harnessing an existing Fall such as Niagara, or by building a dam across a river valley
where land can be had at a reasonable price. The transmission line, therefore, becomes an essential part of most hydro-electric schemes.