Showing papers on "Transient (oscillation) published in 1973"
01 Feb 1973
TL;DR: In this article, a mathematical model suitable for the analysis of traveling-wave phenomena in underground power-transmission systems is presented, which can be applied to the solution of steady-state problems or, by means of Fourier-transform techniques, to solution of transient problems.
Abstract: A mathematical model suitable for the analysis of travelling-wave phenomena in underground power-transmission systems is presented. The model is developed in terms of a generalised angular frequency, and may therefore be applied to the solution of steady-state problems or, by means of Fourier-transform techniques, to the solution of transient problems. The model takes into account skin effect in the conductors and in the soil. It is then shown how the system model may be analysed using multiconductor-transmission-line theory to give the transient response of the cable system. The wave-propagation characteristics are given for the natural modes of a certain cable system. These characteristics are examined with a view to their implications on transient phenomena.
363 citations
TL;DR: General expressions are presented to describe the transient in a multi-enzyme sequence in which the initial enzyme is rate-limiting, revealing that the initial enzymes does not contribute to the transient but does determine the steady-state velocity.
127 citations
TL;DR: There are many kinds of digital calculation methods for transient phenomena on a electrical system and the most highly developed technique among them is the iterative method of travelling waves which has been given as the O'Alembert's solution of the wave equation as mentioned in this paper.
Abstract: There are many kinds of digital calculation methods for transient phenomena on a electrical system. The most highly developed technique among them is the iterative method of travelling waves which has been given as the O'Alembert's solution of the wave equation. The technique was first devised by Schnyder! and Bergeron\" and developed by Frey3 , Barthold , McElroy 5, Ametani\" and others. The other famous technique is the Fourier transform which is based on the Bernoulli's solution of the wave equation. This technique has been developed by Leg0 , Mullineux\", Wedepohl? and others. This, however, has a severe disadvantage, that is, computer programs are using hundreds of hours of computer time with procedures requiring N 2 operations to compute Fourier transforms of N data points.
85 citations
TL;DR: In this paper, a method is described for determining the structure and coefficients of dynamic models of turbogenerators from detailed equivalent circuits of the d-and q-axes of a solid rotor generator.
Abstract: A method is described for determining the structure and coefficients of dynamic models of turbogenerators from detailed equivalent circuits of the d-and q-axes of a solid rotor generator. These models are intended for analyses of power system dynamics in cases where it is desirable to have a very accurate representation of the synchronous machine. The models have been used to study power system hunting or dynamic stability, first swing or transient stability, load rejection overvoltages, resynchronization of cross-compound turbine-generator sets, field current and voltage during out-of-step operation, voltage dip and other phenomena associated with machine operation on power systems. The paper reviews some of the experience obtained in system studies and in comparisons between test results and computer simulations.
59 citations
TL;DR: TIAs can now stand on their own as an important, and, at times, unique aspect of symptomatic cerebrovascular disease, distinct enough to warrant a textbook in its own right.
Abstract: TIAs can now stand on their own as an important, and, at times, unique aspect of symptomatic cerebrovascular disease, distinct enough to warrant a textbook in its own right. With new information on a worrisome and serious natural history, growing knowledge of risk factors and their management, sophisticated neuroimaging techniques, and a broadening armamentarium of therapeutic approaches, the clinician is now faced with multiple levels of decision making. Does one admit the patient with a recent TIA to the hospital? What are the optimal imaging and diagnostic strategies? What antiplatelet agent to use? What is the role for surgery and interventional techniques? How do I optimally control associated risk factors?
47 citations
TL;DR: In this article, a numerical procedure is presented to deal with solution of transient free-surface flows in porous media, which is shown to be stable and suitable for this class of problems with the aid of a digital computer.
45 citations
35 citations
TL;DR: In this paper, a non-iterative method of solving the algebraic equations involving only direct matrix multiplication is discussed. But the results of computer tests on a complex multi-machine system demonstrating the importance of load modelling and the effectiveness of the new proposed non-interactive solution technique are presented.
Abstract: Techniques are developed for improving the speed of solution of transient stability studies which include the effects of synchronous machine amortisseur circuits and nonlinear variable-voltage loads. A fast, non-iterative method of solving the algebraic equations involving only direct matrix multiplication is discussed. Results of computer tests on a complex multi-machine system demonstrating the importance of load modelling and the effectiveness of the new proposed non-iterative solution technique are presented.
32 citations
TL;DR: A digital model for the application of analyzing the primary pressure transient of nuclear power plants is presented and can be used as a design tool for pressurizer vessels and associated pressure control devices.
Abstract: A digital model for the application of analyzing the primary pressure transient of nuclear power plants is presented. No restrictive assumptions have been made, and a rigorous treatment of the cons...
27 citations
TL;DR: In this paper, the Frank-Kamenetskii parameter is used for both common and unusual shapes using isoparametric finite elements to describe the geometrical features of the bodies.
Abstract: Steady-state and transient ignition problems are solved by the finite element method. Discretized equations for the reactive heat equation are set down using Galerkin's method. The steady-state discretized euqations are solved by an incremental Newton-Raphson procedure using the Frank-Kamenetskii parameter as the incremented or ''loading'' variable. Critical values of the Frank-Kamenetskii parameter are given for both common and unusual shapes using isoparametric finite elements to describe the geometrical features of the bodies. The transient ignition problem is solved by using the finite element spatial description together with a midinterval time differencing scheme.
TL;DR: The results of experiments and calculations suggest that photoconduction of the sapphire substrate accounts for most of the observed "excess" currents internal to these circuits - while gas ionization effects are significant at the external device terminals as discussed by the authors.
Abstract: Silicon-on-Sapphire (SOS) construction reduces junction photocurrents to such low levels that other radiation-induced currents tend to dominate the response of an SOS circuit to transient ionizing radiation The results of experiments and calculations suggest that photoconduction of the sapphire substrate accounts for most of the observed "excess" currents internal to these circuits - while gas ionization effects are significant at the external device terminals
01 Sep 1973
TL;DR: In this article, a method of calculating the unbalance response of flexible rotors from a modified Myklestad-Prohl technique is discussed in connection with the method of solution for the transient response.
Abstract: The equations of motion necessary to compute the transient response of multi-mass flexible rotors are formulated to include unbalance, rotor acceleration, and flexible damped nonlinear bearing stations. A method of calculating the unbalance response of flexible rotors from a modified Myklestad-Prohl technique is discussed in connection with the method of solution for the transient response. Several special cases of simplified rotor-bearing systems are presented and analyzed for steady-state response, stability, and transient behavior. These simplified rotor models produce extensive design information necessary to insure stable performance to elastic mounted rotor-bearing systems under varying levels and forms of excitation. The nonlinear journal bearing force expressions derived from the short bearing approximation are utilized in the study of the stability and transient response of the floating bush squeeze damper support system. Both rigid and flexible rotor models are studied, and results indicate that the stability of flexible rotors supported by journal bearings can be greatly improved by the use of squeeze damper supports. Results from linearized stability studies of flexible rotors indicate that a tuned support system can greatly improve the performance of the units from the standpoint of unbalanced response and impact loading. Extensive stability and design charts may be readily produced for given rotor specifications by the computer codes presented in this analysis.
01 Feb 1973
01 Aug 1973
TL;DR: In this paper, the effects of the frequency dependence of the cable parameters, as well as the multiconductor aspect of the travelling-wave problem, were investigated for the generation of transient sheath overvoltages.
Abstract: In a previous paper, the theory of natural modes was applied to power-cable transmission systems to analyse steady-state and transient effects which were of significance to power-system engineers. In the present paper, using this theory as a basis, computer results are given for transient sheath overvoltages resulting from the application of a unit step of voltage between the conductor and the sheath of one of the cables of an underground power-transmission system. The results are derived from a mathematical model which includes for the effects of the frequency dependence of the cable parameters, as well as the multiconductor aspect of the travelling-wave problem. The results obtained lead to an explanation of the generation of transient sheath overvoltages in terms of well defined modes of propagation. This forms the basis of a qualitative method for predicting transient sheath voltages up to, and slightly beyond, the first peak value. The method becomes quantitative once the `universal' curve defined in the text is known.
TL;DR: In this article, a mathematical treatment for the transient behavior of a disk electrode when the potential is varied is given, and the characteristic time constant for decay of the double-layer capacity is assessed.
Abstract: A mathematical treatment is given for the transient behavior of a disk electrode when the potential is varied. The characteristic time constant for decay of the double-layer capacity is assessed. 2 figures, 1 table.
TL;DR: In this article, mathematical models of varying complexity for the digital computation of transient behaviour of generators and motors in a synchronous power system, and their application in the light of extensive studies which have been made on a model power system.
Abstract: This paper describes mathematical models of varying complexity for the digital computation of transient behaviour of generators and motors in a synchronous power system, and their application in the light of extensive studies which have been made on a model power system. The computed and measured responses to transient disturbances are compared and the representation of terms in the equations which substantially affect behaviour is discussed.
TL;DR: In this paper, an out-of-reactor simulator was developed that simulates both in-Reactor thermal gradients and heating rates in oxide fuel pellet stacks through direct electrical heating, and preliminary results of tests of both steady-state and transient operation indicate that fuel phenomena and fuel microstructures similar to those observed in actual inreactor transients can be produced.
Abstract: An apparatus has been developed that simulates, out-of-reactor, both in- reactor thermal gradients and heating rates in oxide fuel pellet stacks through direct electrical heating. Preliminary results of tests of both steady-state and transient operation indicate that fuel phenomena and fuel microstructures similar to those observed in actual in-reactor transients can be produced. (6 references) (auth)
TL;DR: In this article, an asymptotic series is described suitable for the evaluation of the early time response in a transient problem, where the solution in the frequency domain is known in certain forms of ascending series of frequency (including optical, diffracted, and creeping waves).
Abstract: An asymptotic series is described suitable for the evaluation of the early time response in a transient problem. Once the solution in the frequency domain is known in certain forms of ascending series of frequency (including optical, diffracted, and creeping waves), asymptotic formulas are developed to "translate" it readily into the time domain.
Journal Article•
TL;DR: In this paper, an out-of-reactor simulator was developed that simulates both in-Reactor thermal gradients and heating rates in oxide fuel pellet stacks through direct electrical heating, and preliminary results of tests of both steady-state and transient operation indicate that fuel phenomena and fuel microstructures similar to those observed in actual inreactor transients can be produced.
Abstract: An apparatus has been developed that simulates, out-of-reactor, both in- reactor thermal gradients and heating rates in oxide fuel pellet stacks through direct electrical heating. Preliminary results of tests of both steady-state and transient operation indicate that fuel phenomena and fuel microstructures similar to those observed in actual in-reactor transients can be produced. (6 references) (auth)
TL;DR: In this paper, the power spectrum of a stationary time series of interest is estimated using existing cross-spectral programs and shown to be insensitive to brief transient signals imposed on the series.
Abstract: We indicate an estimate of the power spectrum, of a stationary time series of interest, that is insensitive to brief transient signals imposed on the series. In the case that no transient is imposed, all that one loses by computing the estimate is two degrees of freedom, asymptotically. The estimate may be computed using existing cross-spectral programs.
TL;DR: An entirely digital method of measuring angular speed, acceleration, and torque during transient characteristics is described in this article, where Diffraction gratings are used in an optical transducer which is interfaced to a digital computer to process the data obtained and to provide a plot of the transient characteristics as functions of time.
Abstract: An entirely digital method of measuring angular speed, acceleration, and torque during transient characteristics is described. Diffraction gratings are used in an optical transducer, which is interfaced to a digital computer to process the data obtained and to provide a plot of the transient characteristics as functions of time.
TL;DR: In this paper, the mean square response exceedance characteristics of a single-tuned system to amplitude modulated noise were investigated and the results bear on the accuracy of spectral estimates of nonstationary data and relate directly to the design, analysis, and testing of structural systems in environments as gusts, earthquakes, and ignition transients.
Abstract: Discussed are the mean-square response exceedance characteristics of a single-tuned system to amplitude modulated noise. The results bear on the accuracy of spectral estimates of nonstationary data, and subsequently, relate directly to the design, analysis, and testing of structural systems in environments as gusts, earthquakes, and ignition transients. For noise correlated as an exponentially damped cosine, the nonstationary response may exceed its stationary value by a factor in excess of two. A time-varying shaping filter explanation is offered for this behavior. For white noise, such exceedances do not occur.
01 Feb 1973
TL;DR: In this article, the capability of such a system for improving turbogenerator transient performance for both large and small disturbances is investigated. And the performance capabilities of excitation control are also considered for comparison.
Abstract: The availability of electric governors and the provision for continuous control over the turbine interceptor valves, in addition to the high-pressure-steam valves, present a readily controllable, fast-response turbine-power-output system. This paper looks at the capability of such a system for improving turbogenerator transient performance for both large and small disturbances. The performance capabilities of excitation control are also considered for comparison.
TL;DR: In this paper, the results of a series of 249 switching tests including two fault tests were made on the American Electric Power (AEP) 330 km (204 miles) Jefferson to Dumont 765-kV line.
Abstract: This paper reports on the results of a series of 249 switching tests including 2 fault tests that were made on the American Electric Power (AEP) 330 km (204 miles) Jefferson to Dumont 765-kV line. Steady state and transient period overvoltages are examined and analyzed. Comparisons are made with transient network analyzer (TNA) studies performed prior to the tests. Use of nonlinear resistors to drain the trapped energy after opening the circuit is also discussed.
01 Dec 1973
TL;DR: In this paper, the effect of variations in winding parameters from some assumed stator/rotor allocation on the transient performance of a 5.6 kW induction motor has been investigated and a response equation was derived that expresses the severity of the transient current or torque, or the runup time, in terms of a nominal response, together with contributions derived from the parameter variations.
Abstract: Previous work on the transient performance of induction motors has paid little attention to the effect of variations in winding parameters from some assumed stator/rotor allocation. This paper shows that, based on factorialdesign considerations, a response equation may be derived that expresses the severity of the transient current or torque, or the runup time, in terms of a nominal response, together with contributions derived from the parameter variations. The coefficients of the response expressions for the transients that follow several switching and reswitching operations of a 5.6 kW motor are given. The errors introduced by the use of a fractional factorialdesign plan are shown to be small, and mention is made of typical situations in which the technique described may be useful.