Chicago World's Fair — Plutos

World's Fair Electrical Plant.†

BY R. H. PIERCE.

4000 Of all the cities that have ever been built, there has never been one in which electricity has played such an important role as in the White City.

The present exposition is the first international exposition in which electricity has been recognized as one of the great departments, and no previous electrical exhibition has equaled the electrical exhibit of the World's Colombian Exposition.

Volumes have already been written upon the various electrical exhibits, and all that will be attempted in this brief paper is a description of the great plant which furnishes the electrical service of the exposition.

The electrical plant comprises a local telephone exchange, complete systems of police signal and fire alarm service, and the plant for furnishing electric power and light.

TELEPHONES.

The telephone exchange is a regular exchange of the Bell system. It comprises at present 130 telephones. It supplies service for the offices of the officials, the engineers and superintendents. It forms an adjunct to the fire alarm service, and connects the headquarters of the police department, the department of admissions, and of the secret service with all gates and with all portions of the grounds. It contains no points of novelty, but is an interesting exhibit of a great private exchange. It is installed with complete metallic circuits of double and twisted rubber covered conductors. The circuits comprise 150 miles of No. 18 B. & S. wire, and the service is practically unaffected by the proximity of the immense number of circuits carrying currents, both direct and alternating, and all degrees of current strength.

POLICE AND FIRE SIGNALS.

The police signal and fire alarm systems comprise 137 fire alarm boxes of the Gamewell Fire Alarm Telegraph company, and 137 police boxes, and 50 watchmen's patrol boxes of the Police Telephone & Signal company.

These systems are too well known to need even comment, and make the service uniform with that of the city of Chicago, to which it is connected.

The boxes are distributed about the grounds and buildings in pairs, each fire alarm box having a corresponding police box. The number of boxes is estimated to be sufficient for protecting a city of 150,000 inhabitants, and its installation consumed 80 miles of No. 14 B. & S. rubber covered wires.

The watchmen's patrol boxes are located under the floors of the main buildings and enable the guard to send in an alarm direct to headquarters without even the loss of time required to reach the nearest fire or patrol box.

LIGHT AND POWER PLANT.

The portion of the plant which especially commends itself to the interest of both the engineer and the architect is the plant for electric lighting and electrical transmission of power.

All the electrical machinery for furnishing light and power is located in machinery hall, so that the power plant in machinery hall is a great central station. I say "central station," but in fact, the plant is divided, as far as operation is concerned, into nine distinct central stations, each of which, under normal working conditions, is entirely independent.

The plant comprises 98 direct current series arc dynamos, having a total capacity of 5,230 lamps of 2,000 nominal candle power each, fourteen alternating current incandescent dynamos having a total capacity of 128,000 lamps of 16 candle power, one direct current incandescent dynamo having a total capacity of 800 kilowatts and 20 direct current power generators, having a combined capacity of 2,936 kilowatts or 3,935 electrical horse power. In addition to these, there are also four direct current generators, having a total capacity of 600 kilowatts or 804 electrical horse power, which serve the double purpose of supplying current to operate the electric fountains and to charge the storage batteries for the electric launches. There are also one direct current generator of 700 kilowatts or 938 electrical horse power, which operates both arc and incandescent lamps; and, finally, one direct current generator of 180 kilowatts, and one of 45 kilowatts, a total of 225 kilowatts, or 300 electric horse power, which supply the current for search lights. The entire plant has a generating capacity of 14,916 kilowatts or 19,989 electrical horse power, so that it would require not less than 25,000 indicated horse power to operate all the dynamos to their full working load.

CIRCUITS.

The circuits from all dynamos are carried under the floors of the power plant to the several switchboards, and thence under the floor to the gallery, which runs the entire length of the power plant, and under the aisle directly north of the plant. This gallery is for the greater part of its length 13 feet wide and 9 feet high, and is shut off from the rest of the basement on both sides by walls of expanded metal and cement. Along each side of the gallery is a row, and down through the center are two rows of cast-iron uprights placed thirty feet apart. These uprights have sockets into which are driven oak cross-arms. These arms carry from four to six pins. and have, in all, sufficient pins and insulators for 280 wires, allowing but one wire to an insulator, but, by the use of a special two-wire insulator designed for this purpose, the capacity of the gallery is greatly increased.

From this gallery, the circuits are carried out of machinery hall in the main subway and the duct trunk line. All the circuits feeding the east portion of the park are carried in an underground tunnel called the main subway.

SUBWAY.

The main subway, as it passes under the east end of machinery hall going north, is a double tunnel, each half of which is constructed as follows: A series of frames are built of 3 inch by 8 inch timber, and are covered on the outside, on the top and sides, with two inch plank. On the inside, the top and sides are covered with expanded metal and plaster, and the floor is formed of Portland cement. This forms a practically fireproof tunnel, 6 feet 6 inches wide and 6 feet 5 inches high. To the timbers on both sides of each tunnel are lagged cast-iron uprights thirty feet apart. These uprights carry on each side of the subway 12 five-pin cross-arms 2 feet 3 inches long, so that one can walk in a two foot passage having on either side a regular underground pole line. Conductors are carried on double petticoat insulators, there being capacity in the entire subway for 240 insulators. Here, as in the gallery, many two-wire insulators are used. The subway is lighted by incandescent lamps and drained by hand pumps located at low points. Where single insulators are used, all wires are rigidly separated and not less than five inches of air space is allowed.

The main subway runs due north to electricity building, where the west half enter the building, and then branches, running to the mines building, and the east half makes a right angled turn, running east to the bridge over the north canal. The circuits are then carried under the bridge, and on the east of the bridge the subway is continued to the southwest corner of manufactures building, whence, decreased in section, it runs north the entire length of the manufactures building, under the west loggia. It then runs east to a point north of the center of the manufactures building, thence north to the government building. Under the government building it is constructed with a covering of expanded metal and plaster, both inside and out, and from the government building it is continued to the fisheries building, where it ends.

DUCT TRUNK LINE.

The circuits feeding the west half of the Park and Midway Plaisance, with the exception of the power circuits, are carried from the gallery under machinery hall to the north side of machinery hall in a conduit of three and four inch vitrified tile ducts. Thence the duct trunk line is continued by 30 ducts of pump log of 2 1/4 inch bore. Large manhole boxes 30 inches by 36 inches are set every 150 feet. This trunk tine runs under the terminal tracks to the southwest corner of transportation annex, whence it runs parallel to the fence, to a point near the north end of the California state building.

From the main subway and duct trunk line, the circuits are distributed throughout the grounds in wooden ducts of 2 1/4 inch bore. These ducts form a net-work all over the park, and are intersected at angles and convenient points by manholes with cast iron covers. There are in all about 100 miles of these ducts, and about 3,500 manholes.

Thus all circuits are carried underground except those south of machinery hall and along fences. These are carried on poles, while the power and telephone circuits on the west side of the park are run under the structure of the elevated intramural railway.

Having indicated the general arrangement, I will describe as briefly as possible the plant, taking up the different kinds of service in order:

For the purpose of description, we will divide all the dynamo electric machines into two classes. First, exposition dynamos, or machines furnishing service to the exposition and operated by the electrical engineering department; secondly, exhibit dynamos, or machines furnishing current to exhibitors in electricity building and operated by the various electrical companies which furnish them as exhibits.

The arc light plant comprises the following machines.

There are therefore 90 exposition dynamos, having a total capacity of 4,750 lights, and 7 exhibit dynamos, having a total capacity of 480 lights, or a grand total of 99 dynamos, having a total capacity of producing 5,230 lights, all of 2,000 nominal candle power. All these dynamos are regular direct current series machines, and are equipped with standard switchboards and appliances of the respective systems.

In addition to the foregoing, there are, in the terminal station, 160 six ampere arc lamps, and 228 three ampere lamps, equivalent to 164 lamps of 2,000 nominal candle power. There are also 351 Helios arc lamps attached to the incandescent circuits, most of these furnishing lights to exhibitors and to the concessionaires in the Midway Plaisance.

The grounds are lighted by 1,421 lamps, of which 1,308 are upon ornamental iron lamp posts, and the remainder, which light the fences and the south grounds, upon 40 foot wooden poles.

The grand total of all arc lamps in the plant at the present time is equivalent to 5,362 lamps of 2,000 nominal candle power. The outside circuits are all carried underground, excepting those south of machinery hall and along the fences. In the duct trunk line and in all underground ducts, the conductors are of No. 8 B. W. G. rubber covered safety wire, having an insulation of 1-8 inch para rubber compound, a part having mechanical protection of lead, and the remainder being protected by two tapes wound in reverse. Ninety miles of this wire is used. The circuits in the main subway and in buildings are of No. 8 B. W. G. safety wire, having a covering of 74 mils thickness of rubber and braided. Of this wire there are about 200 miles.

All arc lamps are furnished with opalescent or opal globes. This of course materially reduces the candle power, but by diffusing the light, undoubtedly gives much more uniform and satisfactory lighting than could be obtained by clear or ground globes. The general style of construction, in the buildings consists in suspending the lamps from a No. 9 W. & M. iron wire, the conductors being run from lamp to lamp in the air. The lamps are attached to hangers which are insulated both from the lamps and the line. This method of construction has the advantage of using the minimum amount of wire and doing away with all unsightly loops. It is quickly and cheaply put up and presents a neat mechanical appearance. The lamps on posts and over the aisles in buildings are trimmed with step ladders, except in machinery hall, where they are trimmed from traveling cranes. In certain cases, where the lamps are hung in inaccessible places, a special form of hangers is used, so that, by pulling a cord, the lamp can be disconnected from the circuit and dropped to any desired height, and again pulled into place, without interrupting the circuit. The device also does away with the use of any slack wire.

The grounds and all the buildings are supplied with two entirely independent circuits. One set of evening circuits has single carbon lamps, calculated to burn from dark to the closing hours of the night. The other set of circuits, which comprise about ten per cent. of all the lighting on the grounds, is used for patrol, or all-night lighting.

The feature of the arc lighting is undoubtedly the lighting of the central nave of manufactures building. Here the lights are suspended from five great fixtures or coronas, The space to be lighted is 1,268 feet long and 368 feet wide. The coronas are suspended 140 feet from the floor. The central corona is 75 feet in diameter and carries 102 lamps. The other four coronas, which are equally distributed along the main longitudinal axis of the building, are 60 feet in diameter and carry 78 lights each, making a total of 414 lamps. The coronas, which are made of angle iron, are circular hanging galleries in which the trimmer can walk from lamp to lamp. They are reached by iron ladders from the trusses above. The great arched roof of the building acts as a reflector for the lamps, and the lighting, as it appears to the eye, is absolutely uniform.

SEARCH LIGHTS.

There are at present installed four Schuckert search lights on the four corners of the manufactures building. These lamps are operated from the 180 kilowatt, 120 volt Siemens dynamo in the British section in machinery hall. Two lamps are of 150 amperes, one of 100 amperes and one of 63 amperes. The diameters are respectively 60 inches, 44 inches, 36 inches and 24 inches. The 60-inch lamp on the northwest corner is the largest and most powerful ever built, and gives a beam having an intensity of 104,000,000 candle power.

INCANDESCENT PLANT.

All but a small portion of the incandescent lighting of the exposition is supplied from the Westinghouse plant. This plant comprises twelve 10,000 light dynamos, six of which are directly connected to 1,000 horse power engines and six are belt driven, and two 4,000 light dynamos, also belt driven.

All these dynamos furnish a current of 2 200 volts electromotive force, and are compound wound. Each 4,000 light machine has its own exciter, but the twelve 10,000 lighters have their fields excited by three 100 horse power exciters which are operated in multiple arc. These machines are all connected to an immense switchboard, which is the most striking object in the electrical plant. This switchboard, which is of white marble, is arranged in two stories or sections. The lower, or dynamo board, controls all the dynamos. Each large alternator is a double machine, having two independent armatures, so that the board practically has connections for 26 alternators and five exciters. The three large exciters, which are compound wound for 250 volts, are connected to a three-bar bus system, which feeds the fields of all the large dynamos.

The second story of the board is the circuit board, carrying instruments and switches for forty circuits or feeders, and the whole system is so arranged that any dynamo can be connected to supply current to any of the forty feeders.

The twelve large machines are wound for only 7,200 alternations per minute, thus supplying current which can be used with perfect success in supplying arc lights. Each large machine as before stated, has two independent armatures. These armatures are so connected that the two circuits from each dynamo carry current differing in phase by ninety degrees, so that any of the large machines may be used to furnish current for operating either incandescent or arc lamps, or two phase motors.

The distribution of incandescent lighting is shown in the following table:

The circuits or feeders are calculated for a loss not to exceed 10 per cent., each circuit being provided with a Stilwell regulator, capable of increasing or decreasing the initial pressure on a circuit 5 per cent. All circuits, excepting one, to the south grounds, are run entirely underground. The cables, from the switchboard to converters, are all duplex Waring cables, except in the main subway, where Grimshaw rubber covered wire is run on insulators. All converters are placed in fire and water proof pits just outside the buildings, and the secondary wires are led into the buildings in vitrified tile duct. The largest converter used has a capacity of 200 lights, and nearly all are of that size. Every converter on the ground has its own independent secondary circuit, so that no trouble upon a secondary or inside circuit could ever put out more than 200 lights. The secondary wiring is controlled in all cases by switches and cut outs located at points where wires enter the buildings, and the circuits are, in general, distributed from asbestos lined boxes in which the cut-outs and switches are bunched at centers of distribution. The inside wiring is done entirely with the best grade of Grimshaw rubber covered and taped wire, and the wires are run almost entirely in standard molding or in interior conduit. The lamps, which are of 105 volts, are all the new stopper lamp of the Westinghouse company. The general standard of the exposition lighting for lamps suspended at the ordinary height from the floor is 40 square feet of floor surface per 16 candle power lamp, but, inasmuch as the plant presents almost every variety of an incandescent lighting problem that can be thought of, the intensity of lighting varies greatly, ranging from 18 1/2 square feet per 16 Candle power lamp in the gallery of fine arts, and 7 1/2 square feet per 16 candle power lamp in the smallest gallery, to 3,700 square feet per 16 candle power lamp for the system of patrol lighting under the floor of the manufactures building.

The most novel lighting is the lighting of the tanks in the fisheries building, the aquarium being lighted only by invisible lights shining through the water of the tank.

The most brilliant lighting is the lighting of the gallery of fine arts, where the lamps are placed in reflecting screens around all sides of each picture gallery, the lights being only eight inches from socket to socket for nearly two miles of screens.

The finest lighting is undoubtedly that of the administration building. The lighting of the interior is wonderfully uniform, and, in conjunction with the exterior decorative lighting, forms probably the most difficult and beautiful piece of incandescent lighting ever executed. In the incandescent lighting of the exposition it has been the aim throughout to avoid display lighting, but to secure sufficient and uniform illumination, and, where the lights have been placed for decorative effects, to place them so as to be inconspicuous by day, and to bring out at night the decoration or lines of the buildings. Wall sockets have been largely used, and stiff pendant fixtures have been used but in one building, simple clusters hung from flexible cord being almost universally used. This method of construction proves very satisfactory, and has the advantage of being easily and quickly installed, so as to always present a mechanical appearance. It is easily maintained, and, what is important in an exposition, the position of the lights can be easily and quickly changed without disfiguring or damaging the ceiling.

In addition to this lighting, the Siemens & Halske company, of Berlin, has installed the following incandescent lights:

Wooded Island, 120, 25 candle power; Choral Hall, 1,740 lights, equivalent to 2,462 lamps of 16 candle power; Terminal station, 567 lamps, 16 candle power, being equivalent in all to 3,117 lamps of 16 candle power. This makes a total of all incandescent lamps of equivalent of 68,789 lamps of 16 candle power.

The Siemens & Halske lights an operated from a generator in the German section, machinery hall, having a capacity of 700 kilowatts, and furnishing current to the light mains of 440 volts.

The lamps upon wooded island are operated in series of four, and incandescent lamps in the buildings are operated upon a five wire system with equalizing motors at the centers of distribution. The feeders are of armored cable laid direct in the ground. This plant is interesting as illustrating the difference between European and American practices and is the only plant of its kind in practical operation in this country.

POWER.

Although the electric lighting has been carried out on a scale never before approached in an exposition, it is in the transmission of power that the advance of the art of electricity is most conspicuously shown. With the exception of the power in machinery hall, and a portion of the power in the mines and mining building, all the power which is transmitted from the great power plant is transmitted by electricity, and even in machinery hall electricity operates the great cranes, the elevators, and a part of the main line shafting. Circuits are so arranged that power can be had in any building and in any portion of the grounds. The generating plant in machinery hall comprises the machines shown in the following table:

Making a total generating capacity of 2,289 kilowatts, or 3,070 electrical horse power for exposition use and 515 kilowatts, or 690 electrical horse power for exhibitors' use — a grand total generating capacity of 2,804 kilowatts, or 3,585 electrical horse power.

All the generators, except two 80 kilowatt machines, which supply the power for the elevators in administration building, are regular street railway generators, wound for 500 volts, with a guaranteed electromotive force of 550 volts at full load. Each type of machine has its own independent switchboard, but relay circuits are run between boards, so that, in case of emergency, the feeders from one board can be fed from the generators of another. The circuits are run in the main subway and upon the structure of the elevated railway. The feeders and mains consume 180,000 feet of No. 0000 wire, B. & S. gauge, 19,000 feet No. 000 B. & S. wire, 12,000 feet No. 0 B. & S. gauge, and 24,000 feet No. 1 B. & S. wire. This is exclusive of the distributing mains running to the various motors. All the wire is rubber covered and braided, the No. 1 wire having 3/32 of an inch thickness of rubber, and the larger sizes are covered with 1/8 inch thickness of rubber. The cable is of the make known as the E. M. W.

The motors used by the Exposition company are all supplied by the General Electric company, with the exception of two 150 horse power Westinghouse motors operating shafting in the mines and mining building. Exhibitors provide their own motors of such type as they wish. The applications of electric power are almost universal, as electric motors are used to operate almost every kind of machine in use by the exposition, or displayed by exhibitors.

The distribution of light and power as shown in the tables is exclusive of the electric power consumed in the electricity building. This building consumes all the electricity generated by the machines designated as exhibit machines, the electricity being used for light, heat and power, and for producing the many electrical effects displayed in the electricity building.

ELECTRIC LAUNCHES AND ELECTRIC FOUNTAINS.

The four 150 kilowatt Edison dynamos furnish current for operating the electric fountains in the evening, and for charging the storage batteries of the electric launches after 10 o'clock at night.

Each fountain is illuminated with 19 80 ampere Knowles arc lamps, requiring in all 300 kilowatts or 400 electrical horse power.

The launches, 58 in all, are each equipped with a motor of 4 horse power, operated by a storage battery of 78 cells.

The circuits of both fountains and launches are of Edison underground tubing, and are arranged as a 3-wire system.

INTRAMURAL RAILWAY.

Although it is not a part of the plant in machinery hall, a description of the electric plant would not be complete without a reference to the electric intramural railway. This road is the finest elevated electric railway ever constructed. The station has a generating capacity of 3,700 kilowatts, or 5,000 electrical horse power, including the largest railway generator in the world, rated at 1,500 kilowatts, or 2,000 electrical horse power. The road has 6 1/4 miles of single track, and is installed with a third rail system. The cars are regularly run in trains of four, each having a capacity of 133 horse power, with a speed of 25 miles an hour.

INSTALLATION RULES AND INSPECTION.

The installation of the electrical plant throughout has been carried out according to the rules known as the national code, which was accepted as the standard by the insurance auxiliary committee. This code has been made part and parcel of all specifications and contracts. More than ordinary care has been exercised in inspection. Each large building has had a special inspector, as well as each principal branch of the work. Working plans were made showing the location of every lamp, either arc or incandescent, except where lights were located in exhibitors' spaces or pavilions of which detailed plans could not be obtained, and, in these cases, the plans show circuits up to the cutouts in exhibitors' spaces. The contractors for incandescent lighting were required to submit for approval, in all cases, working plans showing details of cutout boxes, and arrangement of circuits, showing each light, and having marked in figures the length of each circuit and the gauge of the wire. Four prints were made of each plan, the contractor and exposition each keeping one print as a record, the third print being given to the foreman of the contractor as a working plan, and the fourth being given to the exposition company's inspector, whose duty it was to see that the work was installed according to the plan, and national code and in a workmanlike manner. Although the making of complete wiring plans has apparently never been considered necessary by architects, it was found to be the only way in which a work of this magnitude and variety could be thoroughly inspected, and the results obtained were most satisfactory. The inside wiring almost always tested out perfectly clear, with very high insulation, and, when the lights were thrown out by thousands for the first time, the inside wiring was almost absolutely free from "bugs," and if there were any, they were so easily removed, that their presence was never noticed.

Much that would be of interest cannot yet be written, for the efficiency of the various machines is yet to be determined by tests and the length of this paper does not admit of going into details of construction; but I will conclude by enumerating a few points to which I would especially direct the attention of such as may wish to draw conclusions from the inspection of the electric plant.

First. — The great saving of space to be made by the use of the direct-coupled dynamo.

Second. — The advantage of the adoption of a central station system having machines of one type and large, units suitable for supplying both arc and incandescent lights and power service from the same conductors.

Third. — The advantages in series arc wiring of construction and devices which do away with slack wire and admit of more mechanical construction and a neater appearance than is generally obtained in this class of work.

Fourth. — The possibility of, in all cases, doing mechanical work, and at the same time having all conductors accessible.

Fifth. — Advantages to be gained by the use of iron pipes as an interior conduit, not only as a matter of safety but economy.

Sixth. — The advantages of an inspection of electrical work, not merely by making electrical measurement after the work is completed, but by having practical men see that the work is mechanically perfect as the work is being done.

Seventh. — The great advantage of having complete detailed working plans of wiring construction, in order to be sure that the work is properly laid out, and is installed as it is laid out; and in order that the work may be at any time easily maintained and readily changed or repaired by any intelligent workman.

† Read before the World's Congress of Architects, Chicago, August 2, 1893.