Publication: High-Tension Power Transmission
New York, NY, United States
ELECTRICAL POWER TRANSMISSION.
BY CHAS. F. SCOTT.
The national and international expositions held in America mark certain fairly definite eras in electrical development.
In 1876, at the Philadelphia Centennial, the telephone was announced. There was a dynamo which could supply one arc lamp. One of the features of the exposition was a great engine of 1000 hp.
In 1884 an electrical conference was held in Philadelphia. By this time electric lighting was assuming commercial significance. There were numerous stations supplying arc lights and incandescent lights. Some of these were beginning to pay dividends, marking the passage of the electrical industry from the experimental to the commercial stage. Generally speaking, however, the apparatus was crude and inefficient, there were few stationary motors, the railway motor and the alternating current had no commercial significance.
By 1893, the year of the Columbian Exposition at Chicago, electrical matters were assuming an extended engineering and commercial development. Engine-type generators for alternating and direct current were being introduced. The street-railway motor was just beginning to operate cars heavier than the ordinary street car, although the principal thoroughfare in New York city was starting a cable road. Electrical exhibits were in great prominence at the exposition, but, in looking back over a decade, the most striking feature is that certain things which are now so common were there simply as exhibits.
The rotary converter was a curiosity in 1893. It began its commercial work a few years afterward and did not become a very important element in electrical systems until four or five years later. In a discussion upon power transmission at the Electrical Congress held that summer, an electrical engineer from California made this statement: "I wish to say definitely that to the investor in California to-day, the successful machine for long distance transmission of power electrically exists only in the minds of the inventors and promoters, or in some beautiful advertisement." There had been in operation for a few years a single-phase transmission of about 200 kw at 10,000 volts a distance of less than 30 miles for lighting. There were a few plants transmitting power by single-phase synchronous motors at voltages of about 3000. Although polyphase generators were in use, there was no plant transmitting polyphase current at high voltage. I remember distinctly a friend announcing to me during the Congress that it had just been officially determined to use polyphase alternating current instead of direct current for the Niagara Falls Power Company. The contract for the Niagara generators was closed several months later. The Folsom-Sacramento transmission, which I believe may be classed as the first polyphase high voltage system in America, was not undertaken until the following year.
In the Congress of 1904, the section which has to do with electric power transmission deals therefore with a branch of engineering which has had its commercial development within the past decade, and, furthermore, the great bulk of that which has commercial value and engineering interest does not date back more than half of that time.
Approximate statistics show that the apparatus manufactured by the leading American companies for power transmission at 10,000 volts or higher provides for the transmission of approximately 1,250,000 hp, all by polyphase current. These striking figures indicate a quantitative or commercial development, which is, however, no more remarkable than the qualitative or engineering development. The elementary diagram of a power transmission system with generator, raising transformers, transmission line and lowering transformers has been developed into great systems with many power-houses, with networks of high-tension circuits connecting many sub-stations, which in turn have distributing circuits with very exacting requirements. Substantially every element in the system from the generator shaft to the incandescent lamp, or motor pulley, has required the constant attention of the designer and engineer. Generator and transformer design, types of windings and of insulation, switchboard, switches, instruments, protective apparatus, insulators, pins and line construction have all passed through many stages of development since the early plants were installed., Each advance in voltage, each increase in power, each increase of distance, each station or sub-station added to a system has increased former difficulties and has brought forth new ones.
Problems of transmission are not problems which can be solved in the laboratory alone. Apparatus must meet the precise conditions of operation and be judged by experience.
The transmission problem, moreover, is not one pertaining to a single plant. The conditions of climate and of service requirements are varied. That which is successful in one place, and for a given kind of service, may be wholly inadequate elsewhere.
The general engineering problems involved in high-tension transmission are not those for the individual, but, broadly speaking, they are for the engineering profession. We will not succeed by isolation but by cooperation. He who does not contribute to the general fund of experience and he who does not profit by the experience of others is narrow and short-sighted. Competition and rivalry should not limit and restrict progress, but should urge to better attainments. Research and experience, theory and practice must go hand in hand.
Well may we congratulate ourselves upon the progress, both quantitative and qualitative, which has been made in the past decade, but we have reached no limit, no resting place. There is every indication that the growing applications and the demands for power, the enlarging radius which high pressures make practicable will bring more difficult and more exacting problems to the engineer and will lead to results which in future may make our present record simply the small beginnings of what is to follow.
A great impetus was given to the polyphase system when it was adopted by the Niagara Falls Power Company and the selection of 25 cycles, a radical departure from the practice and the prevalent ideas of that time, was effective in making this frequency a recognized standard.
A few facts in connection with the power developments at Niagara Falls are significant and typical. From the first, a large portion, usually the greater part, of the power developed has been consumed by processes or industries which were not yet invented or perfected at the time that the Niagara development was undertaken. The initial installation of the Niagara Falls Power Company consisted of three generators with a combined output of 15,000 hp, although wheel pits were provided for two more units. The first power was delivered commercially in 1895, nine years ago. Extensions have been rapid. This company has generators aggregating over 100,000 hp installed. Another company is developing 25,000 hp electrically, and plants are now under active construction for an additional output of nearly 500,000 hp.
Many of the electrical questions which are of particular interest at the present time are not broad and general, they are specific and in detail, they are with regard to the particular type, or form of apparatus, or method of construction. In recent conferences with the engineers of three transmission systems I found that each had a particular element in his system which was the source of most of his trouble, and yet, in two of the cases the elements most liable to give rise to trouble caused little or no apprehension in either of the other plants. The difficulties in one place may not be the difficulties in other places. Hence the value of free interchange of experience and of data.
A recent writer has said that the cost of a great exposition might well be borne by the general government as there would be value returned through the indirect impetus given to its citizens. Even from the inspiration given to a single individual there might come results which would justify the whole cost. We have come together for interchange of information and of ideas. Fortunate will we be if, supplementing the mutual helpfulness and assistance which is sure to follow, there may be also an outlining and consideration of the problems of the future. It is well to look to the details of our present apparatus and systems, we must be awake also to the discovery of things which are radically new in materials, in design, in method, which may better solve the problems we now have and which may enable us to enter into new fields.
Chairman SCOTT: Let me speak a word on behalf of the officers of this Section. I think the first power transmission which can be considered broadly electric power transmission on a fairly long-distance and definite scale was the one at Telluride, Colorado, a 100-hp. motor operated over a few miles at 3,000 volts. It was my privilege to have much to do with the designing and arrangement of the apparatus and system for that operation, so that I think I take a just pride in having had something to do with the first American power-transmission system. Dr. Bell, our secretary, was at the World's Fair in Chicago on the occasion to which I referred; he was on his way to Redlands, Cal., to put in operation the Redlands plant, which transmitted three-phase currents at twenty-five or twenty-six hundred volts for a distance of eight miles, and was at the time the largest power transmission. A little later, I think the next year, it was he, if I am correct, who started the Folsom-Sacramento plant which I have classed as the first real polyphase high-tension transmission plant. So that among your officers you have the pioneers in the business.
Dr. F. A. C. PERRINE: What was the date of the Standard Consolidated Plant of Bodie?
Chairman SCOTT: At Bodie, Cal., a plant, practically a duplicate of the Telluride plant, was put in operation in 1892 or the beginning of 1893.
Dr. BELL: A few words in reference to the early state of the art may possibly be of interest to some of the members. I remember very well the first start at polyphase alternating-current transmission. It was in 1892 when the two great rival companies were competing commercially, and both of them struggling with the possibilities of transmission. I remember coming that year to take charge of transmission work for the General Electric Co. and finding as a heritage a contract in Walla Walla, in the state of Washington, for a transmission of five miles, to the amount of about 150 horse-power. At that time, 1892, we were practically lacking in this country any means of doing that work. The heritage had come in the, form of a contract for high-voltage direct-current machines and there was at that time in America no manufacturer who would tackle the proposition of making 150 horse-power direct-current machines to transmit power five miles at any kind of efficiency. The proposition as originally brought before me included a 2000-volt machine and there was not a maker in this country who dared wrestle with building a 2000-volt machine of that capacity. The contract had to be filled, and I remember almost the first thing I had to do in taking hold of that transmission work was to find some way of getting out of the difficulty, which was done by using a single-phase lighting machine, 150 kw, at each end, and starting the synchronous motor, which took all the power, by means of throwing the exciters of the two machines at extra high-voltage upon the line and so getting up speed. That plant may be running yet; it was running up to three or four years ago. By the next year, progress had been rapid and the three-phase generators were worked out so that that first Redlands plant was sold in February or March, 1893, and got installed just after the Electrical Congress, without any considerable difficulty. On that occasion, I believe, two three-phasers were commercially worked in parallel for the first time. The plant was sold under a guaranty, stimulated by the engineers of the company of which our honored president has long been the electrical light; a guaranty that required operating in parallel, and I think there was a doubt that lingered in the minds of a good many people as to whether it could be done. A time came when both generators were installed and the president of the company rode up through the canyon on a short hunting trip, and as he went through the station, and saw the preparations made for paralleling the machines, suggested that he would like to see that guaranty fulfilled then and there. I remember taking—not my life but my nerve in my hands, and parallelizing then and there the machines, and, for a wonder, they went together without the slightest difficulty. I say, for a wonder — I knew from experiments in the laboratory they must go together, and I knew perfectly well when they were synchronized they would go together, but confidentially, I may be here justified in saying that the next two or three times we tried to parallel those machines there was trouble. That was the first of the American polyphase plants, if I possibly except a pair of little generators which were then running in Concord, N. H., aggregating 70 kw or 35 kw apiece. They were machines which had been remodeled from the old single-phasers and had surface-wound armatures, giving 500 volts or thereabouts, and the history of the—installation of those two machines may be of interest. Another contract had been taken and was passed on to me at the same time, to-wit: in 1892,— a proposition for transmitting power five miles, in Concord, N. H., for the purpose of running small motors. That contract had been closed with the specification of using two 500-volt generators connected on a three-mire system. After much labor I succeeded in pureuading the agents and the buyers to the point of using three-phase apparatus. Some of the three-phase motors were delivered and it was necessary, prior to the installation of the large machines, which was waiting the completion of the dam, to do something toward supplying customers with motors. The company did not desire to put in any more 500-volt continuous-current motors, so two or three — three, I think, — polyphase induction motors — the first in commercial use in this country — were shipped up there and the two little generators were sent up after them and installed in a steam-driven station. Those, I believe, were actually the first polyphase machines which were in use in this country. Somewhat later, another interesting plant was installed, in Taftville, Conn. It was a duplicate of the Redlands plant, practically, on a five-mile transmission, which is not at all notable but at least interesting as being the first transmission for driving railway generators for street-car service. They were driven in connection with other mill machinery by a 250-hp. synchronous motor, the synchronous motor having auxiliary windings in the field and being started as an induction motor. In connection with that plant some of the early difficulties are forcibly brought to mind. There were no insulators at that time adequate for use as pull-off insulators in keeping up the line, and during one whole afternoon we ran the railway and the mills of 1,700 looms with arcs breaking every few minutes across the insulators at the end of the line, while an industrious assistant of mine, perched on an enormous pile of dirt which had been accumulated in the excavation of the tailrace, was making (to use a Hibernianism) snow-balls out of the dirt and throwing them at the insulators to break the arcs. Such were some of the asperities with which we had to contend in the very early days, but those days were, providentially, soon ended.
Mr. E. KILBURN SCOTT: There is an impression in Europe that the adoption of the polyphase alternating current at Niagara followed directly from the success of the Tivoli-Rome installation. I remember going down to see that particular plant soon after it was started, about 1892, and on signing the register, I remember seeing the names of the members of the Niagara commission. I really believe that the instant and complete success of that particular installation had great weight with them. We have not much to show in England in transmission of power, in the early days, but perhaps I may be allowed to remind you of the pioneer work of Ferranti, when he transmitted power by alternating currents from Deptford to London, eleven miles at 10,000 volts. He proved that it was possible to transmit power at such a high pressure through underground insulated cables. That was a very important thing for us to know. We were not then allowed to run bare high-pressure wires. Our Board of Trade is much more reasonable now, I am glad to say.
Mr. Scott has mentioned that a large amount of transmission work has been done within the last five years, and especially on the Pacific coast. Is not this traceable to the peculiar geographical advantages there/ The very high falls enable you to use the tangential water wheel, which is the most beautifully simple, as well as the cheapest, prime mover in the world. The steam-turbine cannot compare with it.
I am now engaged on a plant in North Wales, where we are using power from a lake on Mount Snowdon, and we have a fall there of 1150 feet; but I do not know of such another case in Great Britain. There are two or three others of 900 feet; but they require expensive hydraulic works to develop them. When I came to work out the details of the Snowdon plant, I was specially struck with the simplicity of a plant driven by high-pressure tangential water-wheels. With high falls, the water is generally pure and free from sand, as well as from organisms that cause growth in pipes. On low falls, the water is much more likely to contain organisms, and machines have had to be invented to scrape out the pipes. On the Pacific coast you have pure water, in some cases from glacial streams, and the reason why so much power transmission has centered there is largely due to those high falls.
Chairman SCOTT: The last speaker mentioned one of the geological conditions which has favored our transmissions in California, namely, the mountain ranges and the high falls. There is another which I think has been equally favorable to water-power development, and that is the lack of coal. The cost of fuel is high and water-power is resorted to as a necessity. I noticed when the pure water of California was mentioned as being the only thing to be found there, that our friend Mr. Hutton looked a little dubious. He appeared to be rather surprised at so general a statement.
Mr. R. S. HUTTON: Regarding the pureness of the water, Mr. Chairman, in the winter time, as in any other good country, we have rain. While our rainy season is rather short we have a fair share of it. A good many of our plants are located at points well down on the sides of the mountains, and above such points in earlier times the sides of the mountains have been considerably gouged out by the hydraulic mining processes. This has filled up a great many of the gulches, and left much debris, which the high water has gradually brought down, a little at a time, until we have in connection with our flumes found it necessary to install a very elaborate system of sand-catching basins, and methods of taking care of the conditions existing. Some of the original water-wheels installed, due to the earlier imperfect design and construction, gave considerable trouble in the matter of cutting of the buckets and parts with which the water came in contact. This to-day has been considerably overcome, so that our wheels give us very little trouble from grit that may be in the water. The nozzles still get some of the effects of the cutting, but this is a small matter and is easily taken care of. Speaking about the high heads we have, just a few days before I left California, we put in operation a 5000-kw unit which, together with its water wheel, forms a very simple and compact design, simply a two-bearing unit, with water wheel overhanging. This unit operates at a speed of 400 revolutions per minute. The head of water used is 1,600 feet and sufficient power is derived from this to drive the generator at considerable over load with a six-inch nozzle. This, as I say, was just put in operation a few days before I left, and we of course do not know precisely what the result is going to be; but from former experience with other units, slightly smaller, we feel that we shall not have a large amount of trouble.
Mr. W. L. WATERS: As modern power transmission usually means three-phase transmission, I think Mr. Kilburn Scott made statements which were to the point when he called attention to the fact that the original polyphase work was done on the other side of the Atlantic. The first polyphase transmission on a commercial scale was the Lauffen transmission at the Frankfort Exposition in 1891, where, I think, 150 hp was transmitted 100 miles, at about 30,000 volts. The work done in the next few years was really single-phase work, and I think I am right in saying that both the Telluride and the Tivoli-Rome plants were single-phase. It was really three or four years later that the Niagara Falls transmission was started up, making the first large important polyphase transmission in this country. Certainly Mr. C. E. L. Brown deserves the credit of the pioneer work in polyphase transmission, and of showing that it was capable of commercial success.
Chairman SCOTT: I should have limited my comment here to work in America; I had that in mind, and in not discussing foreign work I did not mean to belittle it. I will add that limitation in the paper. If there is no further discussion we will adjourn until tomorrow morning.
|Date completed:||February 17, 2007 by: Elton Gish;|