Electric field line

“ In a case in which only mechanical power is wanted at the receiving station, the dynamos and motors concerned in the transmission must have a combined capacity of two horse-power for each horse-power delivered at the motor shaft. In contrast with these figures, the electrical equipment in a transmission with alternating current for mechanical power alone includes two kilowatts capacity in generators and motors, besides two kilowatts capacity in transformers for each corresponding unit of power delivered at the motor shaft unless generators and motors operate at the full line voltage. ”

“ It follows at once from this fact that there must be cogent reasons, apart from the matter of first cost, if the general substitution of steel towers for wooden poles on transmission lines is to be justified on economic grounds. During fifteen years the electric transmission of energy from distant water-powers to important centres of population has grown from the most humble beginnings to the delivery of hundreds of thousands of horse-power in the service of millions of people, and the lines for this work are supported, with very few exceptions, on wooden poles. ”

“ 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. ”

“ Paul and its electric water-power station, on Apple River, the transmission line is twenty-five miles long. The falls of the Missouri River at Cañon Ferry are the source of the electrical energy distributed in Butte, sixty-five miles away. Los Angeles draws electrical energy from a plant eighty-three miles distant on the Santa Ana River. From Colgate power-house, on the Yuba, to San Francisco, by way of Mission San José, the transmission line has a length of 220 miles. Between Electra generating station in the Sierra Nevada Mountains and San Francisco is 154 miles by the electric line. ”

“ If the maximum load that must be carried by a transmission system during a single hour per day requires nearly as much power as can be delivered to the line conductors, either because of lack of water storage or of water itself, even if it is stored, it may be desirable to design these conductors for a small loss at maximum load, rather than to install a steam plant. ”

“ Generators for alternating current can be had that develop as much as 13,500 volts, but such generators cost more than others of equal power that operate at between 2,000 and 2,500 volts. These latter voltages are as high as it is usually thought desirable to operate distribution circuits and service transformers in cities and towns, so that if more than 2,500 volts are employed on the transmission line, step-down transformers are required at a sub-station. ”

“ The electric rock-drill, which can already hold its own with that driven by compressed air, is therefore bound to gain ground in the future. This is a type and indication of what will happen all along the industrial line, the electric current taking the place of the majority of other means adopted for the transmission of power. Even in workshops—where it is [Pg 56] important to have a wide distribution of power and each man must be able to turn on a supply of it to his bench at any moment—shafting is being displaced by electric cables for the conveyance of power to numerous small motors. ”

“ They may be installed and maintained cheaply, solely for generating electricity, if desired. Steam engines, however, require so much care and expert attention that their use for farm electric plants is not to be advised, except under conditions where a small portion of their power can be used to make electricity as a by-product. ”

“ Paul, Minn., about twenty-seven miles long, there are no guard wires for lightning protection. Further east, on the large, new transmission system that stretches from Spier Falls and Glens Falls on the north to Albany on the south, a distance in a direct line of forty miles, no guard wires are employed. On its way the transmission system just named touches Saratoga, Schenectady, Mechanicsville, Troy, and a number of smaller places, thus forming a network with several hundred miles of overhead wire. ”

“ Another advantage of connecting transmission and distribution lines in a sub-station, where regulation of voltage can be had, lies in the fact that it is practically impossible to maintain an absolutely constant pressure miles from a generating plant at the end of a transmission line that is carrying a mixed and varying load. A result is that without the intervention of regulation at a sub-station it is almost impossible to give good lighting service over a long transmission line. ”

“ In some transmission systems the distribution circuits for stationary motors are not fed by the same transmission lines that carry the lighting load, but draw their energy from lines that do no other work. This practice is certainly desirable, as it frees the lighting circuits from all fluctuations of voltage due to line losses with changing motor loads. ”

“ All through that town the lighting and cooking in even the humblest homes is by electricity. The few small factories use no coal or steam-power. In the mountain region over one hundred cities, towns, and rural communities have electric wires in their houses. All are lighted by them and very many have thrown out coal ranges and cook by electricity.
The region is one of mines everywhere, some of them the largest in the world; and nearly all of them have discarded their gigantic steam-, hoisting-, and pumping-engines for electric motors. ”

“ If, now, energy from the water-power is to be transmitted over a distance of many miles, a new set of costs is to be met. In the first place, it will be necessary to raise the voltage of the transmitted energy much above the pressure at the dynamos in order to save in the weight and cost of conductors for the transmission line. This increase of voltage requires transformers with capacity equal to the maximum rate at which energy is to be delivered to the line. ”

“ When a transmission line must carry a load of stationary or railway motors, it is a common practice to divide the line into at least two circuits, [239] and to devote one circuit exclusively to railway or motor work and another to lighting, at any one time. In some cases this division of the transmission system into two parts, one devoted to the lighting and the other to the motor load, is carried out not only as to the sub-station apparatus and the line, but also as to the transformers, generators, water-wheels, and even the penstocks at the power-plant. ”

“ In the railway world there is a growing conviction that the adoption of electric traction on all suburban and inter-urban railways must be simply a matter of time. For main line traffic the possibilities of using electricity are as yet only an article of faith among electrical engineers. ”

“ Less than one horsepower of energy will light the farmstead; less than five horsepower of energy will provide light and small power, and take the drudgery out of the kitchen.
For those not fortunate enough to possess water-power which can be developed, there are chapters on the use of the farm gasoline engine and windmill, in connection with the modern storage battery, as sources of electric current. ”

“ Energy transmitted over long distances must sometimes pass through conductors that are underground or beneath water. In some other cases it is a question of relative advantages merely, whether portions of a transmission line go under water or overhead. Where the transmitted energy must enter a sub-station in the heart of a large city, it not infrequently must go by way of underground conductors without regard to the voltage employed. In some cities the transmission lines may be carried overhead, provided that their voltage is within some moderate figure, but not otherwise. ”

“ Power transmission with continuous current has the advantage that the cost of generators remains nearly the same whatever the line voltage, and that no transformers are required. Such transmissions are common in Europe, but have hardly a footing as yet in the United States. The reason for the uniform cost of continuous-current generators is found in the fact that they are connected in series to give the desired line voltage, and the voltage of each machine is kept under 3,000 or 4,000. ”

“ Except for a few little storage-battery or Diesel generator systems, that couldn't handle one tenth of one per cent of the barest minimum load, it's been the only source of electric current here since 1962, when the last coal-burning power plant was dismantled. ”

“ The fact that a circuit-breaker may be designed to open the line which it connects, whenever the direction from which the flow of energy takes place is reversed, is taken advantage of at some sub-stations to guard against a flow of energy from a sub-station back toward the generating station. By this means a flow of energy from a sub-station to a short circuit in one of the lines or cables connecting it with the generating plant is prevented. ”

“ The greater the total loss of voltage on a transmission line supplying sub-stations that are scattered along much of its length, the larger will be the fluctuations of voltage that must be compensated for at all of the sub-stations save one, under changing loads, if only one circuit is employed between the power-plant and these sub-stations. Suppose, for example, that a transmission line 100 miles long is composed of a single circuit, and supplies two sub-stations, one located 50 miles and the other 100 miles from the power-plant. ”

“ If more than one point of distribution exists on the same transmission line, the regulation at the generating plant must be designed to maintain the desired pressure at only one of these points, leaving regulation at the others to be accomplished by local means. One method of regulation consists in the overcompounding of each generator so that the voltage at its terminals will rise at a certain rate as its load increases. ”

“ Luckily, Austin Ford, the engineer in charge of the hydro-electric plant of the Woodbridge Quarry Company, became interested in the "Scout Engineers," and through him the officials of the quarry company were persuaded to allow the lads to use as much electric current as they required without cost. The youngsters quickly built a transmission line to the electric station, which was located a few miles north of the town on a branch of Otter Creek. ”

“ 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. ”

“ This is particularly true in cases where energy transmitted over a single circuit is distributed for both incandescent lamps and large electric motors, because the starting and operation of such motors causes large fluctuations of amperes and terminal voltage on the transmission circuits. To hold such fluctuations within limits which a sub-station can readily compensate for, it is necessary that the loss in the transmission line be moderate, say often within ten per cent of the total voltage delivered to it at maximum load. ”

“ 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. ”

“ The adoption of electric traction on such a route [Pg 123] as the Brighton main line would be a benefit in several ways. It would lead to a faster express service, as the high overload capacity of the electric motor enables it to take small account of gradients. ”

“ Modern electric stations driven by water-power are usually but one story in height and are clear inside from floor to roof, save for cranes and roof trusses. This construction may be seen in the Niagara, Spier Falls, Cañon Ferry, Colgate, Electra, Santa Ana River and many other notable plants. In spite of this one-story style of construction, the electric stations reach fair elevations because of the necessity for head room to operate cranes in placing and removing generators. ”

“ Even a small water-driven electric station that can be operated by a single attendant at any one time must have two attendants if it is to deliver energy during the greater part or all of every twenty-four hours. But a single attendant can care for a water-power plant of 2,000 horse-power or more capacity, so that two plants of 750 horse-power each will require double the operating force of one plant of 1,500 horse-power. ”