Showing papers in "Transactions of The American Institute of Electrical Engineers in 1907"

Alternating-Current Electrolysis

Abstract: The development of the one-phase railway motor leads to the introduction of grounded alternating-current systems, in which the current is returned over the rail. With rail-return, necessarily more or less current strays through the ground, reaching gas and water pipes, lead cables, etc. When using direct current for railroading, lead cables, etc. are protected against electrolytic corrosion by connecting them to the negative terminal of the circuit, so that the stray current enters the cable from the ground, but does not leave it; that is, the cable is always at a negative potential against ground. With alternating currents this method of protection evidently is not feasible, since the potential difference constantly reverses.

Constants of Cables and Magnetic Conductors

Abstract: In the paper on “Line Constants, Etc.,” equations were given for the inductance and capacity of the parallel conductors used in transmission lines. The formulas given were sufficiently accurate for any transmission line calculations where the distance between wires is large compared with their diameters; where, however, the diameters are comparable with the distance, as is often the case with cable transmissions, it is necessary to use the strictly theoretical expression.

Electrolytic Corrosion of Iron and Steel in Concrete

Abstract: In these days of wide and rapidly growing use of reinforced concrete and hydraulic cements in all kinds of structures, the question often comes up as to whether concrete will afford to iron and steel the same protection from stray currents of electricity that it does ordinary corrosion or rust. In the practice of investigating movements and results of currents upon under ground pipes and other structures, several instances have come to our notice where damage has been caused by electrolytic action upon metals covered or incased in concrete or Portland cement.

The Rowland Telegraphic System

Abstract: Since the invention of the Morse system more than fifty years ago, telegraphy has grown by law of natural evolution to meet the demands of an increasing business. The Morse system has been the measure of the potential of the telegraph wires and of the operator. To handle a continuously increasing business, telegraph managements have been compelled to stretch annually new copper wires and to employ new operators, because the present wire systems have been worked continuously to their capacity and operators to their highest efficiency under the conditions imposed by Morse methods. It is evident that this indefinite extension of wire systems and the force of operators involves the consequent investment of enormous capital and increases indefinitely annual maintenance charges.

Zigzag Leakage of Induction Motors

Abstract: Various formulas have been given heretofore for the predetermination of the leakage coefficient of induction motors, but the results derived from these formulas are so divergent that the formulas themselves are rather discredited. It seems to the writer that the following study about the values of the zigzag leakage may help to clear this somewhat unsettled question.

The Grounded Neutral, with and without Series Resistance, in High-Tension Systems

Abstract: The object of this paper is to raise for discussion the question of grounding the neutral, a question that continually confronts the engineer operating an alternating-current generating, transmitting, or distributing system. The writer wishes to consider this question from the viewpoint of the operating engineer, since it is naturally he who is most interested.

A New Type of Insulator for High-Tension Transmission Lines

Abstract: Link Insulators. Suspension and Strain Type. The transmission of large amounts of power over long distances has reached such proportions that the voltage necessary to transmit this energy makes the problem of line insulation difficult. The so-called “pin” type of insulator has been enlarged to meet the greater demands until it has approached, if not already passed, the limits of good construction. Mr. Buck has given this matter a great deal of study in his high-potential transmission work, and being dissatisfied with the mechanical features of a pin insulator, has devised a method of line construction involving the use of “suspension” and “strain” insulators. The suspension insulators support the line from above, hanging vertically beneath the cross-arm (or other point of suspension). The strain insulators are used at turns and at intervals of say, every mile, to support and “anchor” the line, also as pull-off insulators on curves and to dead-end lines.

The Grounded Neutral

Abstract: During the consideration of the design of one high-tension installation, the question of grounding the neutral was investigated, and resulted in a decision to ground the neutral points of the generators through a limiting resistance. It was my privilege to contribute to that design and to recommend that this resistance be omitted. The reasons for grounding, the reasons for and against the resistance, and facts relatively to operation covering a period of over two years may therefore be of interest in connection with this discussion.

Line Constants and Abnormal Voltages and Currents in High-Potential Transmissions

Abstract: With a large number of the very high voltage transmission systems being planned at present, the information readily available in regard to capacity, inductance, etc., of transmission lines, is not sufficient to pass upon some of the important questions which necessarily will be brought up. Below are given, therefore, the equations from which these constants can be determined.

Underground Transmission and Distribution of Electrical Energy

Abstract: The faults in underground cables naturally classify themselves as follows: 1. Defects in the cable itself. 2. Injury received during installation. 3. Faulty workmanship. 4. Mechanical injury. 5. Electrolytic action. 6. Certain external injuries, the cause of which may not be conclusively established.

On the Substitution of the Electric Motor for the Steam Locomotive

Abstract: The purpose of this paper is fourfold: 1, to record certain facts relative to heavy electric traction which have been established by experience; 2, to present calculations of relative costs of steam and electric traction in railway service based upon these facts; 3, to point out the transcendent importance of standardizing electric railway traction equipment as rapidly as may be consistent with progress; and 4, to raise the question whether a frequency of 25 cycles per second or 15 cycles per second should be adopted in railway operation by alternating-current motors.

Power-Factor, Alternating-Current Inductive Capacity, Chemical, and Other Tests of Rubber-Covered Wires of Different Manufacturers

Abstract: Probably no form of insulating material for wires has been so frequently discussed as india rubber and its component ingredients, known commercially as “rubber.” Very many tests have been devised to determine the percentage of rubber and other materials, and especially the amount of fine para.

Potential Stresses as Affected by Overhead Grounded Conductors

Abstract: This paper is a theoretical investigation of the potential gradients and the equipotential surfaces about grounded conductors suspended in the air, and also about metallic towers for supporting transmission lines. It is obvious that equipotential surfaces surround all conducting material subject to static strain, but the position of these surfaces and the gradient of change at different points are usually difficult to determine.

New Principles in the Design of Lightning Arresters

Abstract: The installation of lightning arresters is of the nature of an insurance. A certain percentage of the cost of the apparatus can reasonably be invested as a safeguard in protecting the apparatus. Furthermore, a percentage of the income can also be invested in protective apparatus as an insurance against interruption of service. The value of uninterrupted service depends upon the nature of the use of the current and will consequently vary in different plants. Plants which make contracts involving penalties for interrupted service naturally put a higher premium on good service. Protecting the insulation of the apparatus has been an easier matter than protecting the continuity of service. It has sometimes happened that the service has been interrupted by the action of the protective apparatus itself. This is especially true in the case of a grounded phase on an insulated delta or Y system.

Interaction of Synchronous Machines; A Graphical Solution by Means of a New Circle Diagram

Abstract: When two synchronous machines are in operation as generator and motor, the amount of power demanded of the motor causes it to assume a definite phase relation to the generator, somewhat dependent also upon their relative excitation and upon the impedance of the circuit including the two machines. When such machines are operating in parallel there is theoretically no power to be transferred, but this ideal condition can only exist when the excitation and phase relation of the machines are identical; if these differ, even by a small amount, transfer of power must take place between generator and motor. The power required by the motor causes a certain vector difference; conversely, the presence of a vector difference points to a definite transfer of power from one machine to the other.

The Heating of Copper Wires by Electric Currents

Abstract: In August 1889, a report was made by one of the present writers 1 to the Edison Electric Light Co., on “The Heating of Conductors by Electric Currents.” The report was published in the minutes of the convention of the Association of Edison Illuminating Companies, at Niagara Falls, August 1889. It contained a large number of measurements of the temperature elevations of active conductors supported in wooden moulding, and in free air, within doors and without. A further report was made in 1893 2 upon the temperature elevations of electric-light cables. The research reported in the present paper has been undertaken to extend the scope of the above measurements, and also to increase the precision of the results previously obtained. In the measurements of 1889 and 1893, above referred to, the temperature-coefficient of resistivity of copper wires was taken as 0.388 per cent. per degree centigrade of temperature elevation; whereas it is now taken by the American Institute of Electrical Engineers as 0.42 per cent. per degree centigrade from and at 0° cent. 3 Again, the law of thermal radiation employed was that of Dulong and Petit; 4 whereas the law of radiation generally adopted at this time is that of Stefan. 5