Showing papers in "Transactions of The American Institute of Electrical Engineers in 1949"
TL;DR: Simple equivalent circuits can be devised for extensive power networks by adopting the viewpoint that in power-flow studies the system generation and loads approach, as an approximation, constant-current quantities.
Abstract: NETWORK ANALYZER STUDIES of power-flow conditions on large interconnected systems frequently require preliminary simplification and reduction of the network because of the limited number of analyzer circuits and sources available. Even in smaller systems which do not exceed the capacity of the analyzer being used, it is sometimes desirable to represent in detail only a portion of the system, simplifying the remainder by use of equivalent circuits for the purpose of speeding up studies on the portion of primary interest. Simple equivalent circuits can be devised for extensive power networks by adopting the viewpoint that in power-flow studies the system generation and loads approach, as an approximation, constant-current quantities. The network being simplified may contain numerous loads and generators, but the equivalent circuit derived by this method retains the identity of only the tie-line terminals or points of interconnection with the detailed setup. The line network of the reduced system is replaced by an equivalent mesh network between retained tie-line terminals. If m is the number of such terminals, this mesh network in general will consist of m (m — 1)/2 branches. The effects of the suppressed generators and loads are reproduced by an equivalent generator or load at each tie-line terminal. An equivalent circuit of this type can be derived for a given system either by analytical methods or by simple tests on an analyzer setup of the complete network which is to be reduced. The equivalent circuit is flexible in that any schedule of internal generation and loads can be reproduced readily without the necessity of repeating the reduction or of making additional tests.
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TL;DR: In this article, the results of a study of the effective a-c resistance of a compact segmental conductor in sizes from 1,000, 000 to 2, 000, 000 circular mils, in air and in steel pipe, with equilateral triangular and cradle configurations, were reported.
Abstract: In recent years, there has been a very great increase in the use of pipe-type systems for long, high-voltage impregnated-paper transmission feeders. Thus, a detailed knowledge of the factors influencing the a-c losses of large size conductors with relatively low skin-proximity effect characteristics is of value to all cable and operating engineers. This paper reports the results of a study of the effective a-c resistance of a compact type of segmental conductor in sizes from 1,000,000 to 2,000,000 circular mils, in air and in steel pipe, with equilateral triangular and cradle configurations. From analysis of the data, an approximate separation is made of losses occurring in the conductor, the outer shield structure and the steel pipe. These component losses are compared with accepted and derived formulas, and application of the data is thus broadened by use of mathematical methods. Based upon the suggested methods of computation, tables are given of losses of cables in steel pipe over a range of conductor sizes and voltage ratings.
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TL;DR: A “tree,” so-called because of its configuration, is a special case of a multiterminal network of relay contacts in which a single input terminal may be connected to one of a number of output terminals.
Abstract: THE RELAY “tree,” so-called because of its configuration, is a special case of a multiterminal network of relay contacts in which a single input terminal may be connected to one of a number of output terminals. The path from each output terminal to the input end of the network passes through contacts on all the relays upon which the network is constructed; and no paths can be connected together. The particular path closed through depends upon the combination of operated relays.
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TL;DR: In this paper, a method for estimating the lightning performance of transmission lines is presented based on the stroke current probability data and takes into account all the line parameters believed to affect the performance materially.
Abstract: A method for estimating the lightning performance of transmission lines is presented in this article. It is based on the stroke current probability data and takes into account all the line parameters believed to affect the performance materially. The curves cover the complete range of transmission line designs.
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TL;DR: In this paper, it has been shown that when a moist soil is subjected to a temperature gradient, the moisture will have a tendency to move in the direction of heat flow, which is of considerable interest in cable heating studies because the thermal conductivity of the earth in the heat field involved will decrease as moisture is lost.
Abstract: IT HAS long been known that when a moist soil is subjected to a temperature gradient, the moisture will have a tendency to move in the direction of heat flow. This phenomenon is of considerable interest in cable heating studies because the thermal conductivity of the earth in the heat field involved will decrease as moisture is lost. It is of like interest in the heat pump using a buried ground coil, where migration has also been observed.
TL;DR: In this paper, a series of tests made in the period 1938 to 1942 to determine in the laboratory the effects of lightning strokes on the safe operation of aircraft were described, and the tests showed that the probability of damage from lightning strokes to airplanes of sufficient magnitude to prevent further operation and to result in loss of the airplane is extremely small and can be discounted.
Abstract: The paper describes a series of tests made in the period 1938 to 1942 to determine in the laboratory the effects of lightning strokes on the safe operation of aircraft. Due to wartime restrictions, publication was deferred. Investigated were: the burning of holes in the metal skin of planes and other metallic parts of planes; damage to airplane fuel tanks; breaking of safety glass in windshields; the effect of current flow on ball bearings; effect of impulse sparks on the vision of pilots; and tests on nonmetallic airplane parts. The tests showed that the probability of damage from lightning strokes to airplanes of sufficient magnitude to prevent further operation and to result in loss of the airplane is extremely small and can be discounted.
TL;DR: In this article, it was shown that feedback can be used to equilibrate the magnetomotive force of the a-c windings so that the control circuit can supply only the force required to saturate the core.
Abstract: SATURABLE reactors, in their simpler forms, have been used in controlling many types of equipment. As is known, control is effected by adjustment of the reactor impedance with d-c premagnetization. The a-c windings are so connected that no fundamental component of power-frequency voltage appears in the d-c control winding. For optimum utilization of the core structure, the control winding must supply premagnetization equal to the sum of the magnetomotive force of the a-c windings and the magnetomotive force necessary to saturate the core. Generally, the control winding consists of many turns of fine wire. As a result, a high voltage can be induced in the control winding if one a-c coil becomes inoperative and the effective inductance and time delay of the control circuit are substantial. However, these factors can be reduced if feedback is used to equilibrate the magnetomotive force of the a-c windings so that the control winding need supply only the magnetomotive force required to saturate the core. Consequently, saturable reactors with feedback, or magnetic amplifiers, have been applied in many cases where simple saturable reactors would have been unsuitable.
TL;DR: In this paper, it was shown that the distorted curve shapes of natural oscillations can be rigorously derived from the saturation characteristic of the oscillatory circuit by means of simple integrations.
Abstract: It is shown that the distorted curve shapes of natural oscillations can be rigorously derived from the saturation characteristic of the oscillatory circuit by means of simple integrations. The natu-ral frequency is not constant as under linear conditions, but varies greatly with the amount of saturation. For forced oscillations, a concise dif-ferential equation is given covering all possible cases by only four parameters. The solution can be evaluated for any initial conditions by a straight-forward step-by-step construction. It shows graphically strange curve shapes of flux, current, and voltages, of no regularity with respect to periodic repetition or sym-metrical behavior during the transient state. In the steady state, a rigorous lineariza-tion of the differential equation allows considering the effect of saturation quan-titatively as a distortion of the impressed voltage. The final effect on magnitude and curve shape can be evaluated by repeated superposition of the residual dis-torting voltage. Intense higher har-monics are produced in this way. Consideration of the resistance voltage as actually present in the state of free oscillations shows that natural oscilla-tions can be sustained in true resonance by an impressed voltage of definite magni-tude and curve shape, requiring in series circuits a highly peaked voltage curve. Hence, the saturated circuit can respond to any constituent harmonic of this shape, leading to the forced development of sub-harmonics to the frequency of the supply voltage within certain ranges of its magni-tude. If the ohmic resistance is small a multitude of such subharmonics and all their higher harmonics may develop.
TL;DR: The United States Navy has always been a major user of d-c power as mentioned in this paper, and even after the introduction of 440-volt alternating current into the Navy with installations on the Farragut-class destroyers in 1932, there was still a continued use of a sizable amount of direct current.
Abstract: SINCE THE FIRST installation of electric power on board the USS Trenton in 1883, the United States Navy has always been a major user of d-c power. After the introduction of 440-volt alternating current into the Navy with installations on the Farragut-class destroyers in 1932 there was still a continued use of a sizable amount of direct current. All vessels having a-c systems required some direct current for powering excitation supplies, searchlights, battery chargers, and interior communications. Although alternating current had become the accepted standard, smaller vessels, such as landing craft and patrol craft, retained d-c systems in the interest of simplicity. Other vessels, such as large tenders, repair ships, tugs, and submarines, had relatively large d-c power plants installed for electric propulsion purposes.
TL;DR: In this article, a simple, reliable, and compact optical shutter which utilizes a Kerr cell as a light valve is described, which can be made sufficiently positive and accurate to permit initiation of operation at any preselected instant with a precision of 5×10-9 seconds.
Abstract: This paper presents the theory and describes the development of a simple, reliable, and compact optical shutter which utilizes a Kerr cell as a light valve. With the aid of such a shutter, routine photographic studies of electric discharges have been made using an effective exposure time of 0.000,000,04 second. The novel feature of an electro-optical or Kerr cell shutter is that there are no mechanical moving parts, the speed of operation depending only upon the rapidity with which a required voltage can be applied to the Kerr cell electrodes. These electrodes are immersed in a fluid which exhibits uniaxial birefringence when under the influence of an electric field. Electrical birefringence is described and explained at some length and the optical transmission of a Kerr cell shutter as a function of applied voltage is derived and plotted for reference. With the advent of the ``all-electric'' shutter, some of the latest techniques of the electronic art become applicable to photographic work. The control can be made sufficiently positive and accurate to permit initiation of operation at any preselected instant with a precision of 5×10-9 second. This excellence of control has made possible the detailed photographic study of light from very rapidly changing self-luminous objects. The complete components of an electro-optical camera are described in some detail. Prints are included which show photographic records of the electrical vaporization of a fine wire taken with an effective exposure time of 0.000,000,04 second.
TL;DR: In this paper, the theoretical and practical aspects of a series of attenuation and delay equalizers developed for the L-1 coaxial system are described and an indication of the precision required in manufacture in order to meet the close tolerances of television or long telephone circuits is given.
Abstract: This paper describes the theoretical and practical aspects of a series of attenuation and delay equalizers developed for the L-1 coaxial system. Attention is focused on the adjustable attenuation equalizers and the delay equalizers. An indication is given of the precision required in manufacture in order to meet the close tolerances of television or long telephone circuits.
TL;DR: M ULTIFREQUENC¥ pulsing is a form of signaling with alternating current, which permits the rapid transfer over telephone trunks of the information required to select switch paths in local, toll, and tandem dial telephone systems.
Abstract: M ULTIFREQUENC¥ pulsing is a form of signaling with alternating current, which permits the rapid transfer over telephone trunks of the information required to select switch paths in local, toll, and tandem dial telephone systems. The multifrequency pulses consist of different combinations of two, and only two, of six frequencies. These six frequencies are spaced 200 cycles apart, from 700 to 1,700 cycles, inclusive. Each combination of two frequencies represents a pulse, and each pulse a digit. The pulses are sent over the regular talking channels and, since they are in the voice range, are transmitted as readily as speech. There are 15 pairs of frequencies possible from the group of six; ten of them are used for the digits 0 to 9, inclusive, and one each for signals indicating the beginning and end of pulsing. The remaining three possible pairs are available for future requirements. The multifrequency system is arranged so that if more than two frequencies are received by the equipment, the operator who is setting up the connection receives a flashing cord lamp; then she must lease the connection and start making the call over again in accordance with her instructions. The first multifrequency pulsing system was installed at the toll board in Baltimore, Md., to permit the toll operators to complete calls to local crossbar offices without the aid of another operator, and without the use of senders in the toll office. 1V£ultifrequency pulsing next was used in connection with the new toll crossbar office installed in Philadelphia, Pa. In this installation calls were received over toll lines from distant points, as well as from switchboards within the city, by means of the mulfifrequency pulsing system. Today, installations of multifrequency pulsing arrangements are being made in many cities throughout the United States.
TL;DR: In this article, the authors describe a new multiplexing system employing time division, which features pulse amplitude modulation with a filtering arrangement for minimizing the required transmission bandwidth, and discuss channelizing, synchronizing, transmission equipment, and system performance data.
Abstract: The paper describes a new multiplexing system employing time division. The system features pulse amplitude modulation with a filtering arrangement for minimizing the required transmission bandwidth. The distortion and crosstalk requirements for commercial applications are met over transmission paths including radio relay repeaters. A discussion of the channelizing, synchronizing, transmission equipment, and system performance data is included.
TL;DR: In this paper, a series of studies on the steady state stability of conventional and long-distance transmission systems as influenced by the presence of voltage regulators and other control devices is presented.
Abstract: This paper represents the first of a series of studies on the physical and mathematical analysis of the steady-state stability of conventional and long-distance transmission systems as influenced by the presence of voltage regulators and other control devices. As a first step attention is restricted to the transmission line as a component part of the over-all system and practical equivalent circuits are established for its representation, when the connected synchronous machines oscillate. For that purpose the basic equations of stationary networks are set up when viewed from uniformly rotating reference frames. An isolated inductor and capacitor, then a transformer, and finally a transmission line are used as examples. Their equations viewed from a simultaneously rotating and oscillating reference frame are given in reference 1.
TL;DR: Application of Laplace transform theory to the case of relay-type control yields the response expressed as a series of terms from which the system behavior may be found, and is applicable to any controlled object whose unilateral transfer function can be written.
Abstract: THE METHODS of analysis and synthesis of linear servomechanism loops have been developed to the point where they have become a common and useful tool. Comparable advances have not been made in the case of relay-type control although the latter is of great importance in many engineering fields. The reason for this failure is that the differential equations governing a relay-controlled system are nonlinear in nature and cannot be solved by conventional means. Nevertheless, it is possible to analyze such a system by accepting something less than a finite analytic expression for the solution of the governing differential equation. Application of Laplace transform theory to this problem yields the response expressed as a series of terms from which the system behavior may be found. The information obtainable in this manner indicates whether the system under consideration is stable or unstable and gives relations among the circuit parameters which must hold if the response of the system is periodic. This method is not restricted to cases of intermittently applied constant torque as in previous treatments but is applicable to any controlled object whose unilateral transfer function can be written, as for example a motor, a vacuum-tube circuit, or a complete servomechanism loop.