Showing papers on "Transient (oscillation) published in 1971"

Electrical transients in power systems

Abstract: Fundamental Notions About Electrical Transients. The Laplace Transform Method of Solving Differential Equations. Simple Switching Transients. Damping. Abnormal Switching Transients. Transients in Three-Phase Circuits. Transients in Direct Current Circuits, Conversion Equipment and Static Var Controls. Electromagnetic Phenomena of Importance Under Transient Conditions. Traveling Waves and Other Transients on Transmission Lines. Principles of Transient Modeling of Power Systems and Components. Modeling Power Apparatus and the Behavior of Such Equipment Under Transient Conditions. Computer Aids to the Calculation of Electrical Transients. System and Component Parameter Values for Use in Transient Calculations and Means to Obtain Them in Measurement. Lightning. Insulation Coordination. Protection of Systems and Equipment Against Transient Overvoltages. Case Studies in Electrical Transients. Equipment for Measuring Transients. Measuring Techniques and Surge Testing. Appendices. Index.

Temperature relationship in continuous culture

Abstract: The steady-state and transient behavior of a chemostat-type continuous culture of Aerobacter aerogenes was investigated with special reference to temperature. Experimentally determined kinetic parameters of the fitted steady-state model were found to be strong functions of temperature. The transient response of the culture to a step change in temperature exhibited a dynamic lag whose magnitude depended on the nature and direction of step change.

Direct method for transient stability studies in power system analysis

Abstract: This paper deals with recent advances in developing direct methods for studying the transient stability problem of single-machine and multimachine power systems. The paper starts out with the construction of the mathematical model that is usually employed in the analyis of power system transient stability. Computer simulation methods are then briefly discussed, and it is indicated why accurate direct methods for transient stability investigations would be most welcome. It is shown that the classical direct methods, which are based on energy considerations, can be derived and generalized by means of Lyapunov's second method. The main purpose of the paper is to give an exposition of the interesting results that have been obtained by applying Lyapunov's second method to the transient stability problem of single-machine and multimachine power systems. In the final portion of the paper some areas for further research are discussed.

Transient Currents Induced on a Metallic Body of Revolution by an Electromagnetic Pulse

Abstract: A numerical technique is presented that may be used to predict the current induced on a thin metallic body of revolution excited by an electromagnetic pulse. Examples are given. Introduced here is the use of the radiation condition in a finite difference solution. This development alleviates the requirement that finite difference techniques be applied to a bounded region of space.

Transient Response Characteristics of Capacitive Potential Devices

Abstract: Full voltage line to ground fault tests are performed on typical potential devices and the subsidence transient recorded. To show the worst case of residual voltage, faults are initiated while the primary voltage is passing through crest and zero.

Transient stability of power systems containing both synchronous and induction machines

Abstract: A method is described of calculating the effect of large induction motors on the transient performance of a multimachine power system under fault conditions. The representation of an induction motor is similar to that used for synchronous machines, and is therefore suitable for describing composite systems. The method is based on Park's equations and, unlike earlier methods, allows for the ‘deep-bar effect’ usually present in large cage induction motors. The most accurate result is obtained by using the full set of equations, but more approximate methods using simplified equations are considered. The method is verified by tests on model machines connected by impedances representing transmission lines. Preliminary tests were made on a simple system comprising an induction motor connected to an infinite busbar through an impedance, and were followed by tests on a composite system containing a synchronous machine and an induction motor connected in parallel parts of the system. The results slow that good results are obtained with the accurate calculation which, however, requires a large amount of computer time, but that any approximation introduces considerable error.

Programmed waveform power inverter control system

Abstract: A multi-phase programmed pulse waveform generating inverter control system for controlling power switches to provide transient free electric power to a critical load in synchronism with a utility power source.

Transient performance of reluctance machines

Abstract: The object of the paper is to build up a general picture of basic features of the transient behaviour of reluctance machines to serve as a guide to both the designer and the user of these machines. Consideration of transient behaviour focuses attention on the importance of the rotor winding, and attention is given to the digital solution of the differential equations of the machine, in which each rotor circuit is individually represented. Comparisions are then made with measured performance characteristics, and also with results based on the simple 2-coil representation of the rotor circuits. This simple model is used in demonstrating various features of the transient characteristics, including initial switching transients, asynchronous torque pulsations and their relationship to the average asynchronous torque/speed characteristic, responses to suddenly applied loads, and the effects of load, inertia, supply voltage and rotor-cage design on synchronising performance.

Determination of the Thermal Conductivity of Toluene-A Proposed Data Standard-from 180 to 400k under Saturation Pressure by the Transient Hot-Wire Method I. The Theory of the Technique

Abstract: The theory of the hot wire method of fluid thermal conductivity measurement is reviewed in detail and extended where necessary for application to an experimental system. Particular attention is given to assessing the size of approximations introduced in setting up the mathematical model of the cell which relates the observed quantities to the fluid thermal conductivity.

Direct Methods for Transient Stability Studies in Power System Analysis

Abstract: Absfruct-This paper deals with recent advances in developing direct methods for studying the transient stability problem of singlemachine and multimachine power systems. The paper starts out with the construction of the mathematical model that is usually employed in the analyis of power system transient stability. Computer simulation methods are then briefly discussed, and it is indicated why accurate direct methods for transient stability investigations would be most welcome. It is shown that the classical direct methods, which are based on energy considerations, can be derived and generalized by means of Lyapunov’s second method. The main purpose of the paper is to give an exposition of the interesting results that have been obtained by applying Lyapunov’s second method to the transient stability problem of single-machine and multimachine power systems. In the final portion of the paper some areas for further research are discussed. I. INTRODUCTION T HE PROBLEM of transient stability of power systems becomes increasingly important as t,he size of the interconnected areas becomes very large. Indeed, the tendency of a system to lose synchronism and disintegrate, and the resulting possibility of oscillations in the power transfer between interconnected areas is much more prevalent for large systems than it is for relatively small isolated groups. Optimum control and stability investigations are presently used to a large extent in the analysis and design of power systems. A comp1et.e survey of the application of optimum control to power systems wa.s presented at the 1968 Joint Automa.tic Control Conference [l]. It is the aim of this paper to give an exposition of recent results and mbthods concerning the transient stability problem of power systems. The writing of t.his paper is motivated on one hand by a desire t.0 expose this problem to the cont,rol audience at large, and on the other hand by the timeliness of illustrating an area of application for sophisticated stability analysis techniques to a practica.1 real-world problem. This is done in the hope that such an exposition could. lead to a contribution in bridging the well-publicized gap between t.heory a.nd practice. r\’ot,e that, even in the optimization of t,he steadystat.e operation of power systems [I], stability crit,eria are important, since they const,itute some of the opthizat,ion constraints. In recent yem a large amount of papers on stability has been published in t,he automatic control literature. The applicat,ion of these ideas and methods to actual

Apparatus for the remote detection of conducting bodies utilizing electromagnetic waveforms exhibiting abrupt discontinuities

Abstract: In an apparatus for the remote detection of ore bodies, comprising means for radiating a primary electromagnetic waveform exhibiting abrupt discontinuities, means for discerning secondary signals induced in and reradiated from a conducting body together with transient components of such secondary signals, and means for sampling and examining the transient components, the transient components are processed serially and applied to a signal averager providing a number of channels the outputs from which correspond to the respective time average values of sequential portions of the transient wave form.

Optimum Control of a Turbo-Generator Including an Exciter and Governor

Abstract: A previous paper (1), has shown that a second order optimising algorithm can be applied to a simple model of a turbo-alternator to determine the optimum control inputs under transient conditions. This paper extends the application of this algorithm to a more detailed model including exciter and governor control loops. It is shown that suitable controls can be found to improve the transient performance of a large turbo-alternator, even in the presence of practical constraints on the control system.

Series Capacitor Switching to Quench Electromechanical Transients in Power Systems

Abstract: A method of quenching transient oscillations of a generator feeding a load over long lines was implemented in the laboratory. A disturbance that caused instability was repeated with this control, and the system remained stable.

Transient temperature distributions in cylindrical arc columns following abrupt current changes

Abstract: Using the shock wave technique, radial distributions of gas temperature have been measured in cylindrical, wall stabilized, arc columns under both steady state and transient conditions. The arc atmosphere was air and the current range 0?5-100 A. The transient measurements included the case of free recovery following sudden current interruption. The temperature profiles have been used in conjunction with published electrical conductivity data to determine electrical conductance values and these show good agreement with direct electrical measurements and theory. This result confirms that the arc plasma is in approximate thermal equilibrium so that the column behaviour may be described solely in terms of thermal processes. The importance of natural radial flow under transient conditions has been estimated by calculating flow velocity profiles from the measured temperature distributions and published gas density data. The results are in good agreement with theory, and show the increasing importance of the radial flow at higher currents.

Transistor logic circuit

Abstract: A transistor-transistor logic circuit employing a Schottky barrier diode connected across the output of the multi-emitter input transistor and the reference potential to suppress transient overshoot by controlling the voltage at the collector of the input transistor of the TTL circuit