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Showing papers on "Transient (oscillation) published in 1968"




Journal ArticleDOI
TL;DR: In this paper, a device to provide a signal proportional to changes in generator speed has been developed by Ontario Hydro and field tests have been performed to demonstrate that use of this signal with a high-speed rectifier excitation system results in dynamic stability limits which approximate those which can be obtained with a zero reactance generator.
Abstract: A device to provide a signal proportional to changes in generator speed has been developed by Ontario Hydro. Field tests have been performed to demonstrate that use of this signal with a high-speed rectifier excitation system results in dynamic stability limits which approximate those which can be obtained with a zero reactance generator. Transient stability limits are greater than those obtainable with high-response conventional excitation systems. Results from the field tests and a computer study are compared.

111 citations


Journal ArticleDOI
TL;DR: In this article, a closed-form expression for the transient solution of the Stokes's problem is presented, where exponentials and error functions of a complex argument are provided.
Abstract: The motion of a semi-infinite incompressible fluid caused by the sinusoidal oscillation of a plane flat plate is termed Stokes's problem. When the plate starts from rest in a still fluid a transient solution must be added to Stokes's well-known steady-state result. This paper presents a closed-form expression for the transient solution. Previous answers have contained a non-standard integral which could not be evaluated. The answer presented herein contains exponentials and error functions of a complex argument. These functions are readily available in newer mathematical tables. Graphs of the transient solution are presented for both sin (T) and – cos (T) boundary conditions. Velocity distributions in the fluid are also plotted and it is found that the transient period is essentially complete in one-half cycle for the cosine oscillation and in a full cycle for the sine wave case.

88 citations




Journal ArticleDOI
TL;DR: In this paper, it was shown that the overvoltages caused by energization or reenergization of lines can be made so low that the limiting factor determining how much the line insulation may be reduced might become the over voltage produced by single line-to-ground faults.
Abstract: When the improvements in extra-high- oltage power circuit breakers now being studied are realized in practice, over- voltages caused by energization or reenergization of lines can be made so low that the limiting factor determining how much the line insulation may be reduced might become the overvoltage produced by single line-to-ground faults. On lines insulated for levels below twice the normal line-to-ground crest voltage, such faults could develop into double line-to-ground faults, which would be particularly objectionable if single-pole switching were to be employed.

39 citations



Journal ArticleDOI
TL;DR: In this paper, a digital computer study of synchronous generators which aims to optimize transient stability is described, and alternative excitation controls are investigated, which can produce substantial positive damping of rotor angle excursion without prejudice to the automatic voltage control.
Abstract: A digital computer study of synchronous generators which aims to optimize transient stability is described. Mathematical modeling checked by site tests is used, and alternative excitation controls are investigated. It is shown that the appropriate excitation control can produce substantial positive damping of rotor angle excursion without prejudice to the automatic voltage control.

30 citations


Journal ArticleDOI
J.L. Willems1
01 Sep 1968
TL;DR: In this paper, a Lyapunov function for transient power-system stability was determined for a synchronous machine connected to an infinite bus, which includes pole saliency and damping torques.
Abstract: A Lyapunov function is determined for the problem of transient power-system stability; only the stability of a synchronous machine connected to an infinite bus is considered. It is shown that the obtained Lyapunov function includes governor action, pole saliency and damping torques, and is hence an extension of earlier results.

27 citations


Journal ArticleDOI
TL;DR: In this article, the transient heat conduction in a plate subjected to heating and cooling by combined convection and radiation has been studied, where the plate is assumed to be homogeneous, isotropic, and opaque to thermal radiation.


Patent
29 Feb 1968
TL;DR: In this article, a system for detecting the MECHANICAL state of a machine by converting the vehicular VIBRATIONS OCCURRING in SAID MACHINES into ELECTRICAL VIBRs by means of a pick-up is presented.
Abstract: A SYSTEM FOR DETERMINING THE MECHANICAL STATE OF MACHINES BY CONVERTING THE MECHANICAL VIBRATIONS OCCURRING IN SAID MACHINES INTO ELECTRICAL VIBRATIONS BY MEANS OF A PICKUP, AND ANALYZING THE ELECTRICAL OSCILLATIONS, WHEREBY TRANSIENT OSCILLATIONS ARE SEPARATED FROM THE ELECTRICAL OSCIL- LATIONS AND USED AS A BASIS FOR DETERMINING THE MECHANICAL STATE OF THE MACHINE BEING TESTED.

Journal ArticleDOI
TL;DR: In this paper, a theory of transient SCLC for saw-tooth voltage pulses has been developed on the basis of M any and R acavy's method, which allows the determination of some parameters of the material, particularly the effective mobility of carriers using special points of transient characteristics.
Abstract: A theory of transient SCLC for saw-tooth voltage pulses has been developed on the basis of M any and R acavy 's method. Expressions have been obtained which allow the determination of some parameters of the material, particularly the effective mobility of carriers using special points of the transient characteristics. Experimental investigation of the transient characteristics of thin-film InCdSSiO x Al heterojunction diodes have been carried out to verify the theory developed for the saw-tooth voltage pulse. The I–V characteristics observed with the help of a curve-tracer at sufficiently fast linear voltage increase exhibit a region of n -type negative differential resistance. The theory is found to be in satisfactory agreement with the experiment in the regions where the solutions are derived in analytical form.

Journal ArticleDOI
TL;DR: In this article, the current density distributions in cylindrical and semi-infinite solid conductors for an applied surface step electric field E, and the density in a flat wide conductor are reported.
Abstract: Practical calculations of transient resistance effects in conductors are reported. Included are the current density distributions in cylindrical and semi-infinite solid conductors for an applied surface step electric field E, and the density in a flat wide conductor. Two analogies are used to yield useful results: thermal diffusion in a cylinder and voltage transients on a semi-infinite transmission line. Results are applied to the calculation of time constants of a transmission line and force build-up in a solenoid.


Journal ArticleDOI
TL;DR: In this article, a first-order perturbation analysis of the continuity, momentum, and energy equations coupled with the generalized Ohm's law was performed to investigate the amplification rates of the transient acoustical response to natural disturbances that may disturb uniform flow conditions in supersonic, constant-area magnetogasdynamic generators.
Abstract: A first-order perturbation analysis of the continuity, momentum, and energy equations coupled with the generalized Ohm's law permits an investigation of the amplification rates of the transient acoustical response to natural disturbances that may disturb uniform flow conditions in supersonic, constant-area magnetogasdynamic generators. Fluctuations in the electrical conductivity and Hall parameter are primarily responsible for wave growth or decay due to their dependence on the fluctuating gas temperature, pressure, and density. The dispersion relation resulting from a one-dimensional plane wave traveling in the axial direction is a cubic equation with complex coefficients which is solved numerically for a typical set of steady-state operating values, in the diagonal conducting wall, Hall, continuous electrode, and Faraday generators. In this investigation, 1) the steady-state gradient terms are not neglected, 2) the adiabatic approximation is not made, 3) the cubic is solved numerically rather than by approximate algebraic expressions, 4) solutions are presented for various disturbance wavelengths, and 5) solutions are presented for all operating external resistivities of interest. Results show that under certain operating conditions the upstream and enthalpy modes can obtain energy from the gas, causing considerable increase in their amplitudes during the time they spend in a typical channel.

Journal ArticleDOI
F.T. Flaherty1
TL;DR: In this paper, the transverse velocity of an ideal string is obtained when the string experiences a point load moving with varying speed, and two cases are evaluated in which the load either accelerates or decelerates through the characteristic string speed.


Journal ArticleDOI
TL;DR: In this paper, the authors considered the transient response of a glass capillary tube to a step change in either pressure or voltage under various external loading conditions, and the resulting time histories of the induced force (voltage or pressure) and the fluid flow and electrical current were solved for.
Abstract: Transient electro‐osmosis of water in glass capillary tubes is treated analytically. The usual selective ion adsorption mechanism is assumed. The analysis is restricted to tube radii greater than about 3 × 10−5 m for which the effects of fluid compressibility and electrical capacitance and inductance are negligible. The problem considered is the transient response of the system to a step change in either pressure or voltage under various external loading conditions. The resulting time histories of the induced force (voltage or pressure) and the fluid flow and electrical current are solved for. A Laplace transform technique is employed. Coupling coefficients are established in the Laplace domain relating the electrical current and fluid flow rate to the electric field and pressure gradient. The cross‐coupling coefficients are shown to obey the reciprocal relations for nonsteady‐state irreversible processes.

01 Dec 1968
TL;DR: In this article, a pendulum undergoing parametric excitation is examined in detail for both linear and nonlinear theory and the effects of initial amplitudes and phasing are determined by state plane diagrams and by analog computer simulation.
Abstract: : As background for the dynamic stability of structures, a pendulum undergoing parametric excitation is examined in detail. Theoretically, transient and steady state solutions were developed here for both linear and nonlinear theory. The linear theory showed the presence of various instability regions, and of 'beats' and 'waviness' in the response. The nonlinear theory showed the presence of various steady state limit cycles including some little known subharmonic resonances at 1/3, 1/4, 1/5 of the forcing frequency. The effects of initial amplitudes and phasing were determined by state plane diagrams and by analog computer simulation. Experimentally, the pendulum was excited and both transient and steady state records were obtained. Good agreement was obtained with the linear theory at small amplitudes and with the nonlinear theory at large amplitudes. (Author)



Journal ArticleDOI
01 Apr 1968
TL;DR: The paper describes some analogue-computer studies in which the steady-state and transient characteristics of an asynchronised synchronous machine are examined from the point of view of power generation.
Abstract: An asynchronised synchronous machine is a combination of a doubly excited synchronous machine and an automatic control system, and it overcomes some of the basic disadvantages inherent in a synchronous machine. The paper describes some analogue-computer studies in which the steady-state and transient characteristics of an asynchronised synchronous machine are examined from the point of view of power generation.

Journal ArticleDOI
01 Jan 1968
TL;DR: In this paper, the effect of varying regulator gains on transient response is investigated with the help of gain-locus diagrams on a gain plane, and the Runge-Kutta method with fourth-order approximation is used to determine the transient-stability limit of the same system for various gains.
Abstract: The paper presents a case for correlating transient response with transient-stability limit of power systems. An elementary power system provided with fast acting voltage regulators using various feedback signals is analysed in detail. The effect of varying regulator gains on transient response is investigated with the help of gain-locus diagrams on a gain plane. The Runge-Kutta method with fourth-order approximation is used to determine the transient-stability limit of the same system for various gains. The gains which give good transient response are compared with those which give high stability limit. Efforts have thus been made to see whether it is possible to correlate good transient response with high transient-stability limit.


Patent
10 Apr 1968
TL;DR: In this article, the authors present a solid-state circuitry for coupling input signals of relatively long duration to a logic system, the circuitry comprising an integrator which, in response to input signals, provides a ramp voltage to a level detector.
Abstract: Solid-state circuitry for coupling input signals of relatively long duration to a logic system, the circuitry comprising an integrator which, in response to input signals of the proper magnitude, duration and polarity, provides a ramp voltage to a level detector. Improved transient suppression is achieved by employing input signals to provide, after integration, the base and collector drive for an input transistor. The circuitry is also characterized by adjustable turn on and turn off times which may be made symmetrical if desired.



Patent
26 Apr 1968
TL;DR: A circuit for indicating, measuring, and counting transient voltage signal characteristics present in a power supply system including means for sensing the transient signal of a predetermined magnitude, control circuit means for generating first, second and third output signals in response to the transient signals, indicator means responsive to said first and second signals for indicating the presence of said transient signal, indicates the third signal for measuring the width of the signal, and indicates the duration of signal as mentioned in this paper.
Abstract: A circuit for indicating, measuring, and counting transient voltage signal characteristics present in a power supply system including means for sensing the transient signal of a predetermined magnitude, control circuit means for generating first, second and third output signals in response to the transient signals, indicator means responsive to said first and second signals for indicating the presence of said transient signal, means responsive to said third signal for measuring the width of said transient and means responsive to said third signal for measuring the duration of said transient voltage signals.