Incandescent Electric Lighting/Stations
Design and Operation
of
Incandescent Stations.
By C. J. Field.
I Desire to present to you a brief review of the present and prospective future of central power plants in the larger cities, taking as an illustration one of the more recent types, describing its general arrangement, then proceeding to the consideration of its initial cost, earning capacity, output, operating expenses and economy, and, in conclusion, trying to indicate the immediate future development in this class of work.
Central Stations.
The immediate points to be considered and carefully weighed in the designing of central power plant for a large city are many, and they should receive careful survey before any work is proceeded with. We will briefly summarize them as follows:
First—Recognition of the importance of safety and stability in operation.
Second—Obtaining the true economy of output under all conditions.
Third—Installing of plant in a build* dug entirely suited to the working of the same, and as far as human ingenuity can provide, proof against destruction.
Fourth—Adaptability to proper and economical working of the plant.
Fifth—Division of the generating power into the proper number of units for the safe and reliable operation of the plant.
Sixth—Flexibility of system; that is, adaptation to furnishing current for light, power and other sources of revenue, the obtaining of the largest return per dollar invested, and not carrying to excess for the mere sake of engineering in any part of the plant but the obtaining of proper results therefrom.
Seventh.—Not installing the plant for mushroom growth, but laying it out for comprehensive business, thereby securing at as early a date as possible the entire confidence of the invested capital.
A true and careful consideration of these points will prevent trouble later on. Much of the trouble of stations at the present time in their standing with the community is due to neglect of this point, and the majority of their failures as well. We have got to recognize the fact that the public, to a certain extent, have become prejudiced, in a measure, somewhat unjustly; but this is all the more reason for better and more conservative management and giving them good construction. No more inviting field is offered for either investing capital or good engineering than a central station for lighting, power and railway work.
A Representative Station.
I propose to take as a representative type, showing the present development and first-class work, the station of the Edison Electric Illuminating Company, of Brooklyn, which was completed last fall, and is now in successful operation. In the arrangement of this plant there was somewhat of a departure from previous general practice in this line^ the
company trying to secure the benefit of past experience in the larger stations of this class, both in the arrangement and kind of apparatus used, trying to secure at as economical a cost as possible the best plant for the purpose.
The boilers and engines are located on the first floor, the engines being on the front half, and the boilers at the rear, thereby bringing everything in this part directly under the eye of the chief engineer, making it much better than where the boilers are located two or three stories up; this was obtained by spreading out a little more on the ground. The boilers are Babcock & Wilcox's largest type of sectional water-tube boilers. The engines are 300 h.p., compound, horizontal, automatic engines, manufactured by the Ball Engine Company. Each engine is directly belted to two generators.
Ascending to the second floor, we reach the electrical part of the plant. Here are located in the front part of the building, directly over the engine-room, twenty-four dynamos, each with a capacity of 750 ampères and 140 volts. Each dynamo weighs about eight tons. Overhead travelling cranes are installed here and in the engine-room for ready and quick handling of all apparatus. Through the centre of the dynamo-room is located the electrical gallery. From here are con- trolled the workings of all the dynamos and other apparatus, also all outside lines. Everything in connection with handling, generation, and furnishing of current is directly under the eye of one man in this gallery, and from which he has a general view of the dynamo-room floor and the workings of the dynamo, a second man being on the floor to see to the bearings and brushes. From this gallery run all the feeders, which connect into the network of mains, covering over an area of about one and one-half miles square. The ampère meters are located on each feeder, so as to show the load in each part of the district. This plant maintains its distribution and regulation thereof by balancing within itself. No feeder equalizers are here used for feeder regulation; the uniting and tying up of the system, together with the use of the auxiliary bus effects this regulation. All circuits of this plant are underground, there being about twenty-five miles of underground conductors. These have given perfect satisfaction and reliability in their workings, maintaining to-day an insulation on the system as a whole of over half a megohm.
On the rear of the second floor are located the coal storage, water-tanks and feed-water heater. On the top floor we have the offices, supply rooms and workshops of the company. Returning downstairs again we find in the basement ash-pits, smoke flues, pump-rooms, two large coal-storage vaults, giving a total capacity for storage of over 1,000 tons, air-blast for forced draft and other details in connection with the steam plant.
We have, therefore, here, in a building 75 × 100 feet, apparatus and all departments complete for the generation and supply of current and power for a capacity of 40,000 lights, or the equivalent in light and power, and so arranged as to secure, as far as can be foreseen, continuous working of the plant and entire reliability in the furnishing of its current. It is only thus that we can hope to obtain a business and establish ourselves on the commercial basis which gas light companies have placed themselves in the past years, and thereby secure to our stockholders the returns for which they have invested their capital.
Having thus generally outlined this plant, we will now turn our attention to the consideration of other points in connection with it. One of the most important items is the cost of such a plant. I give you below, in round figures, the cost as shown by the construction accounts and estimates:
| Station building, complete, including all fittings, foundations, stacks, furniture, etc. | $100,000 |
| Real Estate | 36,000 |
| Steam plant, including engines, boilers, pumps, heaters, piping, belts, etc | 50,000 |
| Electrical plant, including dynamos and all electrical apparatus, as switches, etc | 40,000 |
| Underground system material | 115,000 |
| Excavation and labor installing same | 35,000 |
| General, including lamps, meters, tools, instruments, engineering and architectural expenses, wiring, services and office furniture | 50,000 |
| Total | $426,000 |
This includes the entire cost for the plant as it stands to-day, which, as far as the building is concerned, is complete for the entire capacity. At present there is installed generating capacity of boilers, engines and dynamos, for one third (⅓) of the final output of the plant. The electrical apparatus is complete for the entire output, with a very few additions in the way of a few switches, etc. The underground lines have a capacity for 20,000 lights. The work necessary to complete the plant for its entire capacity would amount to about $200,000 additional. For this amount there has been obtained here a plant, which is considered equal, if not superior, to any of this class, and at a cost of twenty to thirty per cent, less than is expended for similar ones.
I will take up the next consideration of the operating expenses of such a plant. In order to place the company (m an earning basis we have to secure to start with a certain number of lights or an equivalent in lights and power to clear the necessary general and operating expenses, which will exist regardless of the smallness of the load; in other words, we must have for such a capacity-plant not less than 5,000 lights with an average income of $8 per light per year to clear the general incidental and operating expenses. This figure we may consider as our unit of operating capacity. From this we can figure the increased earnings and profits for the larger number of lights connected. There exists practically a constant ratio of variable and fixed operating expenses. By variable expenses we mean those obtained on a variation in load and increase of business. This includes coal, oil, lamp renewals, and small increase from time to time in the amount of labor employed. The fixed expenses include those items which remain practically constant under varying conditions of income. A careful analysis of all the items covered in these expenses in such a station as this one, gives the following result: That the fixed expenses are seventy-five per cent, of the whole, and the variable twenty-five per cent, approximately; or, in language which may appeal more directly to you, if we double our income or business, we only increase our expenses 25 per cent. This shows that a station's possibilities and profit lie in increasing this business from the unit point.
The average income per light in stations of this class varies in different parts of the country and with different loads. We have obtained a load diagram, taken from this station, which gives a fair idea of the changes and variations here taking place. The maximum number of lights lighted at any time in proportion to the number connected is very good for such -work and shows a good class of business. The load diagram through the day, however, shows a new station on a clear day with a small number of lights lighted, and power work only just commencing. It is this power work that wants attention, and the securing of which means the bringing up of this average load during the daytime to a good paying basis. The curve for the evening hour indicates a good, broad, solid load, which shows the combination of six o'clock business with the addition of a good solid evening load. Many stations after reaching the maximum point around six o'clock, rapidly fall oil and never regain that point again for the evening. Then we have the illustration of clubs, theatres, churches, concerts and residences, lighting after supper, bringing up the load to its maximum point between eight and nine o'clock. The average load for the twenty-four hours, which is about twenty-five per cent, of the maximum is a very fair one, and with the addition of the day load that will come on with the addition of power, it makes a model load diagram. The general run of stations shows an average for the twenty-four hours of from twenty to forty per cent. of the maximum load; the latter figure is very seldom reached. The writer knows of one station in which we have the latter figure, and where, if we eliminate one short half-hour around six o'clock, we have the remarkable showing of seventy-five per cent. average load for the twenty-four hours.
We have taken some remarkably fine indicator cards, which show the workings of the engines of the steam plant in this station. The division of work shown on the cylinders is as follows:
| I. H. P. head end high pressure cylinder | 63 8-10 h. p. |
| I. H. P. crank end high pressure cylinder | 60 2-10 h. p. |
| I. H. P. crank end low pressure cylinder | 59 2-10 h. p. |
| I. H. P. head end low pressure cylinder | 55 2-10 h. p. |
| Making a total I. P. H. | 238 4-10 h. p. |
Having in the above given a general outline of this plant, its cost and operating expenses. I now wish to call your attention to the points in connection with the type of engines, boilers, dynamos, underground system, etc., to be adopted in a station of this class.
Conclusions.
We will first consider the question of the engine. As already stated, in proposing the engine power of a station of this kind, we first have to consider the question of using either the Corliss or high-speed engine. Regarding the use of Corliss engines in a plant of this kind, we are frank to state our objections. Excessive first cost, ponderous machinery, counter-shafting, pulleys, clutches, etc., lead us to believe that these things are unnecessary when the problem is carefully considered from an unbiased standpoint. What we are after is results; not theory, but actual practice. Assume, for the sake of argument, that we can save five or ten per cent, in steam economy; if this is obtained at a cost, the interest of which amounts to more than this, we are obtaining it for no good whatever; furthermore, there are many other problems in electric light stations which we have to carefully consider in this question of steam plant, one of which has been enumerated before, viz., the question of reliability in operation, and always being ready for service. One of the latest types of stations combining arc and incandescent, where we have the Corliss engine in all its perfection of detail and apparatus, is that of the Narragansett Company, in Providence. If one will carefully look over this plant, as I had the pleasure of doing a short time ago with others, and consider all these problems carefully, and then examine & station similar to the Brooklyn one. I think he will be forced to admit this fact. We want to obtain our power as direct from the engine to the dynamo as possible, and at the same time as cheaply, and obtain the best economy under the variable loads we are going to have. We cannot design our plant for that capacity which is reached as shown on our load diagram, for only a short time in the twenty-four hours, but we must so design it to give this result for the average that we have during the twenty-four hours. Even where we have a more constant load, as iii exclusive arc lighting on municipal circuits. I think even here we need to carefully consider the problem as well.
High-speed engines, so called, although they are not in piston speed any higher than the Corliss, but merely in rotative speed, have shown a considerable development and marked advance in the past year, and the next year is going to see even more development in this line. Owing to better workmanship^ better designing and building than formerly, the prejudice which largely existed among old engineers against this type of engine is rapidly wearing away. With the single cylinder engine under variable load, we often obtain poor economy, but, as compared with the Corliss, under similar conditions, allowing for the discrepancy in price, the result is not so disparaging. 'Now they are going further, and building compound and even triple expansion engines of this class. In the Brooklyn station we have the Ball, one of the representative types of this class of engines, being horizontal, compound engines.
These engines are built for high economy and economical work, and the guarantees made on them I think compare favorably with the guarantee on compound Corliss engines; at least, three or four of the manufacturers of this class of engine stand ready to-day to guarantee from 22 to 25 pounds of water per indicated horse power per hour. I do not know of any Corliss manufacturers who are willing to do any better. This is for non-condensing; condensing from 17 to 18 pounds of water per horse power per hour. Engines of this class are as well built now in workmanship, and as reliable in operation as can possibly be desired. Added to this, we have the advantage of direct connection to our generators, avoiding , all the intricacies of shafting, etc., and the unreliability they entail. Tests made at the Brooklyn station have shown that the engines have actually come up to the guarantee made on them, and that the plant there is showing, as compared with single cylinder engines, an economy of coal per unit of output of from 25 to 30 per cent, better. In a station of this kind, the actual coal consumed per unit of output at the dynamos is considerably larger than is shown in a direct test where we charge the engines only with the coal it uses directly. The weekly records from stations of this class charge the horsepower output with all the coal used by the engine, pumps, condensers, well pumps, cleaning fires, blowing-off boilers, etc., and where the former item is about three pounds of coal per horse power per hour, we have in the latter case, making no allowance for the engine running empty, a result fifty per cent, greater than this. Economy in this line, however, is not going to stop at compound engines, as there are being built by at least two manufacturers, triple expansion high-speed engines. (Mr. Field here showed views of such an engine, imported from France by Mr. Edison.)
Something similar to this is what we may obtain to-day, if encouragement is offered, from such engine manufacturers as Armington & Sons, Ball Engine Company, Mclntosh & Seymour and others. We are coming to a recognition of the fact that if we want the high economy we can obtain it as cheaply and as well, not to say more cheaply and better, with an engine of this class as with engines similar to those installed in the Providence station. In guaranteed economy it will equal the Corliss engine, as installed in the Narragansett station, and give it to you under a wider range of load.
In connection with the triple expansion engine mentioned, we have to consider, again, the problem of the dynamos to be used. We can stay as at present, and belt our dynamos, but I believe that the next large incandescent station will not only include compound or triple expansion engines of 300 or 400 h.p., but will also have multi-polar dynamos, one or two being directly connected to the engine. By this I do not mean belted, but direct shaft connection through a flexible coupling. This of course, necessitates the multi-polar machine, in order to secure the output with a slower speed. Engines and dynamos of this type can be installed in the space at present occupied by the engines alone. This means not only economy in building and real estate, but also in operating expenses.
In regard to boilers for such a plant, we do not know that we have any new economy to be hoped for in the near future. All we have to look for at present is improvement in detail of manufacture and the securing of better and dryer steam. We have two classes of boilers prominently before us for this work. We have, in genera], first, horizontal tubular boilers, which we find in general factory use, to a large extent, throughout the country. Where we have plenty and cheap real estate, poorer attendance and moderate steam pressure, this class, in general, fills the bill. We find, however, that they are now even building them to work up as high as 125 pounds boiler pressure. When we come to construction of the boiler plant on expensive city property, where we are cramped for space, we are almost limited at once to some one of the types of sectional water-tube boilers. In the Brooklyn station we are practically limited to the consideration of this class, and have not only 125nbsp;pounds but 150 pounds boiler pressure, and even higher. We have also the advantage of quick steaming under heavy changes in load.
We have to-day brought before us in the underground systems the consideration of what is to most of the companies their most serious problem, in the proper solution of which the best talent is being devoted. In the Edison underground system we have what is generally recognized as the most practical solution for circuits of less than 400 to 500 volts. We here obtain at a premium of cost the most flexible system and local distribution from house to house, which has no equal It enables you to take off services for local distribution from every twenty feet without in any way affecting the insulation on the main line, and being able at any time to disconnect these services and restore the main to its original condition. In any other system we have the problem of splicing and cutting of cables, which, at its best, is bad work. What we desire is not such a high insulation as good mechanical protection. As long as we can hold a moderate insulation with good mechanical protection, that is all we want. In Paris they have used bare copper conductors, supported on porcelain in a concrete conduit. This has worked satisfactorily in the main so far, but, of course, is very expensive. They are now proposing for all their increase, the Edison tubing for this class of work. In any system of cables drawn in we have the selection of a large class of conduits, but to my mind all we need and desire, as I have before stated, is mechanical protection for these cables, and the cheapest conduit that will afford this protection is all that is necessary. What is wanted especially is some system of local distribution for these higher tension circuits. The underground system installed in Brooklyn has a network of underground conductors in the mains and feeders of over twenty-five miles. This entire system is so arranged, distributed and connected in a network that, with a drop or resistance of 1 per cent, on the mains and 10 per cent, on the feeders, we are able to maintain in the system practically a perfect regulation in the distribution of the current. This system stands to-day representing one of the most complete and perfect examples of work of this class. The largest problems that we know of in underground work are the proposed new extension of the Edison Company in New York, and the underground system of feeders proposed to be installed for the West End Railway, of Boston. The copper alone for the latter amounts to over $l,000,000; and this question of the cost of the copper calls my attention to a fact which I desire to notice, that much of tills question of bugbear on copper is uncalled for when we are considering the underground system. The entire copper used on the system in Brooklyn is less than one-fifth of the cost of the underground system first installed.
I do not desire to claim that the ideas for the class of work here represented and described hold or represent all the perfection to be obtained in central station work. There are many points contrary to the ideas here outlined which are very desirable. I have merely tried to call your attention to what I consider good work in this particular line^ and hope that it will result in bringing forth the discussion and additions which are very beneficial in the consideration of these problems in the results to be obtained., and I would only add a tribute to the powerful and mastermind whose work, from the commencement of this field of central station distribution, has covered the leading problems and points, and whose idea* to-day represent much of the good and very little of the bad problems which we have in this work. I refer to Thomas A. Edison, whose work commenced in this field on the old Pearl street station in New York, over eight years ago, when the majority doubted, and but few believed in its successful carrying out; while we find that station, until within the past few months, when it was partially destroyed, successfully working, and even antiquated as it was, earning large dividends. He has still continued actively to impregnate the work with his ideas from that day to this although he has not taken such an active part in its carrying out, hut I think we may see him at no distant day again taking a hand in this work and bringing forth many new ideas in advancing the progress of the future.