Hydro electric power stations

In the Preface to the First Edition of this book it was predicted that the rapid growth of power demands and the rising cost of fuel would lead, in the very near future, to greatly increased activity in the development of our water-power resources. This prophecy has been so fully justified that the standards of that day are in many instances obsolete, and it has been necessary to rewrite practically all of the more important sections of the book.

The rapid advances made within the past few years in hydro-electric engineering have affected both the hydraulic and the electrical elements. It should also be remembered that the increased size of the typical modern power development calls for the adoption of an entirely new point of view in the consideration of the economic problems involved.

One of the most important changes in the hydraulic equipment of the hydro-electric plant has been the introduction of the spreading and hydraucone types of draft tubes and the propeller type of turbine runner.

On the electrical side, the construction of larger and larger units has led to radical changes in design. The concentration of immense amounts of power has created a demand for more rugged switching apparatus, capable of rupturing enormous short-circuit currents. At the same time, modern industrial conditions have made it necessary to adopt higher standards of safety and continuity of service, with the result that very reliable relay schemes have been devised. Many improvements in this class of apparatus have been made within the past few years.

The present volume sets forth the most recent practice along all the lines mentioned above and in all other matters essential to the design and operation of hydro-electric power stations. In view of the thoroughness with which the different subjects have been treated, it is believed that this edition will be of considerable service, both as a text-book for students of engineering and as an aid to operators, engineers and managers of hydro-electric power stations.

The authors wish to take this opportunity to express their appreciation and thanks to those who have so kindly and willingly assisted in this revision with their suggestions and advice. Among these may especially be mentioned Mr. Lewis F. Moody, of the I. P. Morris Company, who has supplied much valuable material for the section on Turbines, and Mr. O. C. Traver, of the General Electric Company, who has similarly contributed considerable material and advice in connection with the section on Relays. The section on Transformer Connections has been taken from a treatise on the subject written by Messrs. E. A. Lof, L. F. Blume, and A. Boyajian, all of the General Electric Company, and the section on Transformer Drying has been contributed by Mr. F. I. Manvel, of the same company.

The use of water power for industrial purposes dates back to very ancient times. Crude current wheels were familiar to the Chinese on the Yellow River and the Hamites on the Nile and Euphrates fully three thousand years ago. These wheels operated entirely by the kinetic energy of the moving water, and the power thus obtained was utilized for raising the water of the rivers for irrigating the arid land and also for grinding corn and other simple applications. Similar current wheels, although necessarily of improved design, have been most widely utilized and, while very inefficient, are still used for minor works designed for irrigation and other purposes in many countries.

The first radical change in the art was the use of channels, by which the water could be conducted and directly applied to undershot wheels. This improvement resulted in the utilization of some 30 per cent of the theoretical water power, and the system maintained its prominence until almost the middle of the eighteenth century, when the overshot wheel was invented by John Smeaton, who showed that if the bucket wheel was changed into an overshot form, its useful efficiency would be increased to over 60 per cent. In this type of wheel the energy of the water was apphed directly through its weight by the action of gravity and yielded a very high efficiency. Overshot wheels were formerly built of great size. One at Laxey, Isle of Man, constructed about 1865 and said to be still in operation, is 72 feet 6 inches in diameter and develops 150 horse-power. A number of overshot wheels are also in use at old mills in the Catskill Mountains in New York State.

The breast wheel, which followed the overshot wheel, was developed in England during the latter part of the eighteenth century and was used for a great number of years. It consisted of a circular drum, having on its periphery a series of buckets, the sheathing of the drum forming their bottom. They were operated partly by gravity and partly by kinetic energy, and the water was applied through a flume and controlled by gates. Below these was located the "breast" which consisted of a concave cylindrical surface of planking, concentric with the wheel. The clearance was very small, thus "preventing the water from spilling out of the buckets until it had reached the lower level. This type of wheel gave an efficiency of about 70 per cent.

The wheel types described above, however, have now been almost entirely superseded by the turbine, and are therefore so nearly obsolete that they may be considered as of historical interest only. While the fundamental principles of the turbine may be distinguished in wheels used in the sixteenth century, the principal developments were made during the last century. In the turbine the water acts mainly by impulse or reaction or both, and the velocity has a definite relation to the head.

In 1823, M. Fourneyron began his experiments on the radial outward-flow turbine, the first example of which was installed at Pont Sur l’Ognon in France, in 1827. Its principle consisted in an outward discharge from a pipe, to a wheel with curved buckets placed outside of the apertures of discharge. The buckets, revolving from the action of the water, finally discharged it at the circumference with its force exhausted. The tube which supplied the water was closed at the bottom by a concave cone surrounding the wheel shaft, which passed up through it in a pipe, so as not to be exposed to the water. This cone was surrounded by a number of guide plates, which directed the water to the buckets in the proper tangential direction.

The axial discharge turbine was first built by Henschel & Son in Germany in 1837. There has always been doubt as to whether this turbine should be attributed to Jonval or to Henschel. Jonval thoroughly described the basic idea in a patent dated 1841, and it is quite possible that he was working on the proposition as early as Henschel. It proved to be far superior to the outward-discharge type and almost entirely eliminated the latter.

The inward-flow wheel, in which the action of the Fourneyron turbine is reversed, was patented by S. B. Howd, of Geneva, N. Y., in 1836, and seems to have been the origin of the American type of turbine. Very great improvements were made, however, in the construction by James B. Francis about 1847, and many regard him as the originator. The Francis turbine of to-day has displaced all other types of reaction turbines, and, with its rapid development, radical departures have been made from the strictly radial inward-flow, with the result that the Francis turbine of to-day is of a combined radial or diagonal inward discharge type. A transition period in the design of turbines occurred between 1890 and 1900, when the turbine was being modified to meet the requirements of electric generator drive, one phase of this transition being an increased complexity marked particularly by the adoption of multi-runner units.

Another change took place in 1911 and 1912, marked by the return to greater simplicity and the readoption of the single-runner vertical turbine. This period also marks the introduction of the metal speed ring built into the concrete substructure, in combination with a concrete volute casing. Since that time this construction has been universally adopted as standard practice for vertical units under low and moderate heads.

After having remained practically stationary in its development for a number of years, the design of reaction turbines has shown a surprising number of changes and improvements within the last three years. The introduction of the propeller type of runner, and of the hydraucone and spreading types of draft tubes, etc., has thus made possible the extension of the range of available speeds, so that extremely high specific speeds are now obtainable with satisfactory efficiency. Although great progress has been made in the attaining of higher speeds, another problem remains to be investigated; this is the extension of the application of these high-speed turbines to higher heads.

The first great water power developments were made in the New England States. The textile industry was destined to expand rapidly and the water power of the streams was its supporting ally. Under this influence, the first great water power was developed on the Merrimac River, in 1822, where subsequently the City of Lowell became a great cotton manufacturing center. Near Lowell there were soon developed the equally prominent water powers on the Merrimac River at Manchester, in New Hampshire, and Lawrence, in Massachusetts. Each of these developments had a capacity of 10,000 to 12,000 horse-power, and each was chiefly devoted to the manufacture of cotton goods, as were the water powers of Cohoes (1828) in New York, and Lewiston (1849), in Maine. The Connecticut River water power at Holyoke (1848) was largely devoted to the manufacture of paper, as were the Fox River powers in Wisconsin, at a later date. The water powers on the Genesee River at Rochester, N. Y. (1856), and on the Mississippi River at Minneapolis (1857), were largely devoted to the manufacture of flour.


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