Electric displacement field

“ A very high degree of insulation is much more easy to attain in transformers than in generator armatures, because the space that can be readily made available for insulating materials is far greater in the transformers, and further because their construction permits the complete immersion of their coils in petroleum. This oil offers a much greater resistance than air to the passage of electric sparks, which tend to set up arcs between coils at very high voltages and thus destroy the insulation. ”

“ As long as each electric system was confined to a single city or town a broken insulator pin could be quickly replaced, and any material interruption of service from such a cause was improbable. Where the light and power supply of a city, however, depends on a long transmission line, as is now the case in many instances, and where the line voltage is so great that contact between a wire and a cross-arm will result in the speedy destruction of the latter by burning, a broken pin may easily lead to a serious interruption of the service. ”

“ This arises in cases where current is consumed during the day for motors, fans, lifts, electric tramways, and other like purposes, and, as the employment of electric energy for these services is rapidly becoming general, no difficulty need be anticipated in the successful working of combined destructor and electric plants where these conditions prevail. ”

“ He therefore thought that it was possible by symmetrical wires placed on buildings, or over whole cities, so to procure an entire protection from atmospherical electricity. If the electric clouds should even enter between the objects protected and the protecting wires, their activity would be greatly diminished, for the wires would become immediately charged, and nearly all the electricity accumulated on their surface without any danger to the protected buildings. ”

“ Examples of such plants are hotels or apartment houses where electric elevators are operated from the lighting dynamos. Boosters are usually driven by electric motors directly connected to them, though any form of driving power may be used.
With the average current passing through the field coil or the exciter, its armature generates a voltage which is equal to that of the system, and in opposition to it. These two opposing pressures balance, and no current flows in the booster field coils. ”

“ The alternating current employed in transmission has such a comparatively low frequency that its self-induction in a choke-coil is small. Increased protection against lightning is given by the connection of several groups of lightning arresters one after another on the same line wire at an electric station. This gives any lightning discharge that may come along the wire several paths to earth through the different groups of arresters, and a discharge that passes the first group will probably go to earth over the second or third [181] group. ”

“ If, then, we define electric displacement as that change which takes place in a dielectric when it becomes the seat of electrostatic energy, and if, further, we suppose that the change, whatever it be mechanically, satisfies certain well-known laws, and that in consequence certain pressures and tensions exist in the dielectric, electrostatic problems can be solved without reference to a charge of electricity residing on the conductors. ”

“ In America, a strong point is made of utilising, as far as possible, all the existing natural conductors that are to be found upon a building, such as gutters, rain-pipes, and other metal surfaces. During a tempest, the opposite electricities of the earth and the air often select, by their inductive influence, a rain-pipe, gutter, metal roof, &c., for the passage of an electric discharge between them, and unless these metallic surfaces are connected with the earth, they are apt to be dangerous. ”

“ We are not able, even at immense expense, to make the earth connections so large as to compete with the conducting power of metallic gas and water-pipes, the total length of which is frequently many miles, and the surface in contact with the moist earth is thousands of square miles. Hence the electric current prefers for its discharge the extensive net of the system of pipes to that of the earth connection of the rods, and this alone is the cause of the lightning leaving its own conductor. ”

“ When a lightning discharge takes place through an arrester the resistance which the arrester offers to a flow of current is for the moment greatly reduced by the arcs which the lightning sets up in jumping the air-gaps of the arrester. Each wire of a transmission circuit must be connected alike to arresters, and the paths of low resistance through arcs in these arresters to the earth would obviously short-circuit the connected generators unless some construction were adopted to prevent this result. ”

“ If the discharge of a stream during each twenty-four hours is just sufficient to develop the electrical energy required in a supply system during that time, the water may be made to do all of the electrical work in one of two ways. If the water-power has enough storage capacity behind it to hold the excess of water during some hours of the day, then it is only necessary to install enough water-wheels and electric generators to carry the maximum load. ”

“ The object of dividing the total air-gap in a lightning arrester for lines that carry alternating current up into a number of short gaps is to prevent the continuance of an arc by the regular generator or line current after the arc has been started by a lightning discharge. As soon as an electric spark leaps through air from metal to metal, a path of low electrical resistance is formed by the intensely heated air and metallic vapor. If the arc thus formed is, say, two inches long it will cool a certain amount as the passing current grows small and drops to zero. ”

“ It may be possible to clear the air of tunnels by simply discharging electricity into the air—the electricity being supplied by Holtz machines, driven say by small turbines—a very handy form of power, difficult to get out of order. Or possibly some hydro-electric arrangement might be devised for the locomotive steam to do the work. I even hope to make some impression on a London fog, discharging from lightning conductors or captive balloons carrying flames, but it is premature to say anything about this matter yet. ”

“ When ground was broken in 1890 for the installation of the first great power plant at Niagara Falls, the engineers in charge of the project regarded the development of even fifteen thousand horse-power of electrical current with grave concern because at that time economical transmission of electricity over long distances was deemed hardly practicable and because the possibilities in the field of electro-chemistry had been to only a slight extent foreseen. ”

“ It seems, however, that grounded guard wires near to and parallel with long aerial circuits should tend to discharge any high electrostatic pressures existing in the surrounding air, and materially to reduce the probability that a direct discharge of lightning will choose the highly insulated circuits for its path to earth. Lightning arresters may conduct induced and direct lightning discharges to earth, without damage to transmission lines, so that both arresters and guard wires may logically be used in the same system. ”

“ Without a stretch of the imagination, we can imagine an ingenious farmer possessing a water-power electric plant building up a thriving business among his less fortunate neighbors, with an "electricity" route. It could be made quite as paying as a milk route.
Connections for charging storage batteries on 110-volt mains
Many communities have water or steam power at a distance too great to transmit 110-volt current by wire economically; and because of lack of expert supervision, they do not care to risk using current at a pressure of 500 volts or higher, because of its danger to human life. ”

“ Remarking upon this casualty, the Telegraphic Journal says that, "so far from being a source of danger, the electric telegraph must be regarded rather as a cause of safety, as a network of lines spread over a country tends to prevent an accumulation of electricity at any particular point, by continually and silently discharging it to the earth. This is particularly the case in districts where every pole has an earth-wire fixed to it, running from the top to the bottom. ”

“ The different kinds of electricity collected and concentrated are stored ready for use in a large building called "The Electric Store-house,"— the electricities, secured in non-conducting pouches, being placed in separate compartments. This is the more necessary, since explosions arise when antagonistic electricities come into contact with each other, and the commingling of sympathetic electricities deteriorates their quality. For that reason care is taken to keep out light. By the electricity of light most other electricities are affected. ”

“ The more uniform the electrical demand becomes, the more fully may the power from a destructor station be utilized.
In addition to combination with electric-lighting works, refuse destructors are now very commonly installed in conjunction with various other classes of power-using undertakings, including tramways, water-works, sewage-pumping, artificial slab-making and clinker-crushing works and others ”

“ This fault has arisen from the failure of lightning-rod men, as well as owners of buildings, to apprehend what constitutes a ground-connection for electricity. If the eye sees the end of the conductor pass a short distance beneath the surface, all the connection necessary is thought to be effected, because "the ground is always wet enough in a shower." In the cities it is customary to connect the rod with the water-or gas-pipes in the street, which makes the conduction perfect. ”

“ With such facts before us, it is fairly easy to predict the still further electrical development of all important centers. There will be more and better light in homes; there will be more and better light in offices and factories, thus greatly lessening the chances for injury or eye-strain. In all industry, great and small, laborious hand processes will be replaced by safely operated electric machinery, while wider use of electric labor-saving appliances will extend into the home. ”

“ In the installations of the future the power will be brought to the material rather than the material to the power. From the ranges or mountain peaks, and also from smaller hills, will radiate electrical power-nerves branching out into network on the plains and supplying power for almost every purpose to which man applies physical force or electro-chemical energy.
The gas-engine during the twentieth century will vigorously dispute the field against electrical storage ”

“ One of the most striking consists in their opening a path for a current of electricity. The electrical discharge, feeble in itself, not capable of lifting by means of a motor a pound weight a foot from the floor, is yet competent to open a path for a current which can set all the trolley cars of a great city in motion. To exhibit this mysterious effect we bring the ends of the electrical current which we wish to excite near each other, but not touching, in a glass tube with thin walls, from which the air has been exhausted. ”

“ In a transmission with continuous current on the other hand, if the prevailing practice of a constant current and varying pressure on the line is followed, the insulation is subject to the highest voltage only at times of maximum load on the system. Lightning is a very real and pressing danger to machinery connected to long transmission lines, and this danger is much harder to guard against in an alternating system than in a system with continuous constant current. ”

“ The application of transmitted water-power in electrical supply has displaced steam as a motive power in many large industrial plants that never would have been operated from steam-driven electric stations. An example of this sort exists at Portland, where one of the motors operated by the electric water-power system, in an industrial plant, has a capacity of 300 horse-power. ”

“ There are a great number of magnificent water power sites, within very easy access of the surveyed route of the railway, all of which can be easily developed to furnish almost unlimited electrical energy. Hydro-electric energy could be developed at any one of these sites within a distance of thirty miles from the road, which would make transmission to points along it, or possibly operation of it actually, by electricity. It certainly assures cheap power for any manufacturing or milling centre which may develop. All these power locations must inevitably become very valuable. ”

“ Even where the power is to be utilized at some point distant from each of several waterfalls, it may be convenient to combine the power of all at one of them before transmitting it to the place of use. This is actually done in the case of two electric stations located respectively at Indian Orchard and Birchem Bend on the Chicopee River, whose energy is delivered to the sub-station of the electrical supply system in Springfield, Mass. At the Indian Orchard station the head of water is 36 feet, and at Birchem Bend it is 14 feet, while the two stations are about 2 miles apart. ”

“ It should be understood that an electric dynamo or battery does not generate electricity, for if it were only the quantity of electricity that is desired, there would be no use for machines, as the earth may be regarded as a vast reservoir of electricity, of infinite quantity. But electricity in quantity without pressure is useless, as in the case of air or water, we can get no power without pressure, a flow of current. ”